Have I failed financially? What is the norm?

You’ve done very well to pull yourself up from your bootstraps (as my old aunt would say) but wealthy or not, it doesn’t cost anything to be a more understanding. Due to circumstances out of my control (ex became an alcoholic when we had young children) my finances and living standards as a newly single mum took an enormous hit. It’s taken years and a bit of fortunate circumstances to finally be able to treat my (now adult) kids to a decent lunch, for years I couldn’t even buy a lottery ticket. Not that long ago I felt very angsty because I went out with a friend and spent £7 on tea and cake, I was kicking myself for my extravagance. But I never felt like a failure, I was just dealing with the hand I had. OP shouldn’t feel like a failure either and I don’t know what you get out of telling her she is.

Are you claiming everything you're entitled to, including disability benefits & being tax efficient, on social tariffs etc? Do you know what's coming in & going out every month? Do you take advantage of deals/offers, loyalty schemes, employee benefit schemes, discounted gift vouchers, cashback etc etc?

I'm with @TheSoapyFrog that you might just need to spell it out. We all have an unconscious bias towards assuming people are more calculating than they actually are. You see your children as adults now which is a different situation to when they were small, but to them they are still themselves and you are still mum who bought them nearly everything they owned their whole lives. And possibly eating out doesn't feel affordable to them yet - successfully "launching" doesn't necessarily mean you have loads of disposable income.

I would approach it that it's fairer to them to bring this to their attention than to "politely" wait for it to occur to them. They're young, they still need some guidance, this is you guiding.

Maybe pay next time but bring up the subject. Explain that it's just too expensive X2. Say I'll get this but how do you want to do it next time, do you want to take turns or shall we split it? Or meet at the park instead.

How old are they @Cantering87
If they are back from Uni I think you are being really unfair
Its always like this in families where there are too many children, the adults blame the older children and call them greedy/ entitled just for wanting normal things
If they are older and working then you need to speak up, you are calling them entitled but it was you who raised them ...

I think this is probably the way to talk to them, you are sad you cant afford to pay for them but thats the reality, rather than blame/ entitled comments
Im sure they will be fine with that

Even if you were absolutely loaded it’s still so embarrassing for your kids to just assume lunch is paid for without asking or ever offering/paying for themselves. Nip it in the bud OP!

Well aren't you lovely?

They are definitely old enough to appreciate why you might not be able to fund everything for them. I think you need to bite the bullet and make the position clear.

This ^

and

I have never set a precedent to pay, I never say ‘I’ll get these.’ They just sit there. The last time we went out I left it an uncomfortably long time to see if they offered to go and order. They just hang back! I know I shouldn’t ask what they’re having but after an awkward age of just sitting there I just always end up saying ‘what do you want?’ because I’m literally walking to the bar or counter

is just odd. They are your dc. Why can't you just communicate with them ?

I have no qualms at all at saying to my dc "Anyone want to join us a X for a meal? It is 'every man for themselves' ". Or I'd have no issue either going to the bar to order for me and the 10 yr old at that sort of pub, or saying to one of the adult dc, 'Can you order them so they arrive together - I'm having the fish and chips and dc wants the nuggets - here's our money' and hand over £25 or whatever covers yours. With the ice creams in the park, mine have been brought up on us nipping into the supermarket for a box of ice lollies so we'd never get to that, but if they wanted expensive ice creams from a van I'd be saying 'Knock yourselves out. I'll wait here with the bags' .

I don't understand how you can be in a situation where you are on good terms with your dc, but not be able to speak openly to them.

I saw a meme the other day that said something like "everything is all inclusive when dad comes" -

Of course it depends on circumstances! I can afford to treat my kids (one at uni, one lives on his own but minimum wage). My uni DD has more ready savings than I do because she’s super frugal, and would rather walk two miles than pay for the bus. She will likely live with me after graduation as we are in London - unless she gets a well paying job I won’t charge her rent, I know she’ll be saving hard for a masters or when she eventually moves out on her own. But I won’t be paying any extras - she’ll pay for all her expenses, so other than food she won’t be costing me much.
My son I treat to a supermarket shop when I visit and if we go out to eat, because he couldn’t afford to eat out. I think it’s money well spent. But as I said, I can afford it!
My parents were quite well off when they passed away. But in our youth my mother had to borrow money on occasion to pay for our school uniforms, and I remember one Christmas we were in a one bed flat (there are five of us) and one sister and I slept in the livingroom. If we had been older and working we would have contributed to our keep for sure!

My PIL have more money than us, so yes FIL typically pays but we never assume, always offer and say thank you! And we reciprocate too. We would never sit in a cafe where you go up to order and just sit there expecting PIL to go up and order and pay for us!

I think it’s about being honest - if you can’t afford it, you can’t afford it. Hopefully your kids appreciate that it is more expensive than ever to go out for lunch. If they’re both working it’s honestly not a crime to not pay for them! Don’t beat yourself up, like I say I think the biggest difference here is the expectation and never ever reciprocating from your kids. You’re worth more than that!

My parents are well off due to a combination of circumstances and could certainly pay for us if we went for a meal out or coffee, but we almost never did that. They live frugally and it wouldn't occur to them (or us) to meet up over something that cost money. We would just go to each other's houses - much cheaper and more relaxing.

Bil (40s) always assumes his parents will pay. It’s so infuriating and frankly embarrassing. He definitely does the waiting it out routine, pops to the loo when the bill is coming, asks for last min add-ons… it’s as subtle as a clown in a lift.
Recently DH and dfil have adopted a mini script of just saying ‘split this three ways’ the second the bill comes. Of course Bil/Sil always order the most expensive drinks, meals, extra dessert etc and have children too… it’s just pure entitlement. If it just us and pils we take turns and don’t keep count.

My parents pay for specific things when we stay (eg the chippy, and some drinks or treats me and DH like). We always bring stuff with us and I usually pay when we are out.

I agree you need to engineer situations where you’ll get yours and the u18, and they sort themselves. Or just make clear that you and u18 have brought snacks but if they want to get xyz go ahead. Let them go first, and make clear you don’t want anything, but then afterwards change your mind and just sort you and u18 after.

Maybe you can also have adult money conversations with them - I cant believe that the mortgage is now up to x; I’ve had to pay x on school uniforms etc; we can’t afford a holiday this year so we are going to do a day trip to the seaside if you’d like to come along I’ll share train times…

also in case you need to hear it - you’re doing great and it’s tough!

How are you at maths? Do you understand things like inflation & how much your earnings need to be constantly rising just to say the same?

I don't mean to be unkind but posters sometimes come on here & say "I've got a decent salary why do i feel poor". And it will emerge they earn under 30k, which these days is not much more than minimum wage. Often their wage hasnt risen much in a decade, and is now worth quite a lot less than it was. People often struggle to fully grasp how much inflation reduces the value of their earnings.

Eg if you earned 30k in 2016, you need to earn at least £42k now just to keep up with cpi inflation. In reality, rpi is higher, plus that inflation rate is a mix of essentials and non essential goods and services and they are constantly messing with the "basket of goods" it is based on. I track prices on my food shopping, fuel & energy rates etc & in my view, inflation on really essential stuff is higher. I think you need nearer 50k to match what a 30k wage bought you in 2016, especially allowing for fiscal drag/higher tax burdens due to tax threshholds not keeping up with inflation.