18 year old son asked for lunch by family member

I think that’s a good idea @EWAB . Be close by in case he needs you and drill into him that he mustn’t sign anything or even verbally agree to anything.

It’s quite possible that she just wants to meet her late partner’s extended family, but you can’t be sure. 18-year-olds who are still at school are used to being guided and advised by older adults so if she did ask him to agree to something, he may assume that it’s ok, when it could actually have negative consequences for him, iyswim.

Dear god. Wtf?
Will you be sitting around the corner when he is married with kids?
How will you know if she gets emotional or weird? Are you going to bug the restaurant?
Do you not think as an adult he could mahage himself?

Has the funeral happened already? Maybe she wants to meet some of his family before. If it’s already happened they why have they not met there. I do find it odd when money is left to someone you’ve never met just because blood

I would tread cautiously. There could be a massive amount of money involved, especially if the late uncle owned property in London.
I wonder if the woman knew about the will or if it's come as a shock to her and she's about to lose what she thought of as her home.
Has she been a carer to the man only to get shafted when he died?
Is she going to be alone?
I would be concerned, OP and I think you should be too.
It might all be quite lovely of course but quite possibly not.

Absolutely not, if your company was required the relation would have invited you too. Are there any circumstances why you think you should attend?

So the elderly relative is the uncle's partner, is she also a beneficiary of the will? Do you suspect she'll try to emotionally blackmail your DS into giving up part of his inheritance?

That’s such a drip feed I can’t even be bothered now!

If my partner was giving money to someone they’d never met I’d be curious to meet them and would also want them to know about my late partner. Doesn’t your son have any curiosity about this man or does he just want to cash the cheque?

Isn't it most likely that she's wanting to tell your son about the man who has left him money in his will? And discover who is going to benefit from her partner's generosity? You say they never met but isn't your son at all interested in him? It does rather come across as if your only concern is money. I would understand more if your concern was that he's too young to be dealing with a recently bereaved woman and wanted to make sure the meeting went ok for both of them.
Edited to say: I've read your update.

Probably would have helped to explain that in your original post, as it makes a big difference to the context.

If you're asking 'Is an 18-year-old old enough to have lunch alone with a much older relative' then the answer is yes, of course he bloody is and it would be weird to insist on going with him.

But if you're asking 'It is possible that a much older relative, who is the partner of someone who has died and left my son a sum of money, might have an ulterior motive involving manipulating him out of his inheritance and should I go along to make sure this doesn't happen' that's a very different question.

Assuming it's the latter, given that your son is an adult (whether you think of him as one or not) I think you need to respect whatever he wants you to do. If he feels awkward, weird or nervous about the whole thing, or he thinks he might find it hard to navigate things if she starts guilt-tripping him or trying to make him sign anything legal, then offer to go with him. But if he's confident he could deal with that if it happened, then he can obviously go alone if he wants. Definitely have a talk with him about it all first.

I think you are being unduly suspicious, OP. Most likely she wants to meet the nephew of her late partner because he used to talk about him, or was fond of him, or she's wishing she had made more effort to get to know the family when he was alive. If you are worried that she might for example want him to hand over his legacy to her, just remind your son that he doesn't know this woman and should listen politely to any requests or suggestions she makes and take advice before agreeing to anything.
If you're worried that she might get emotional, having recently suffered a major bereavement, I'm sure your son will cope, in a public place. Expecting her to be 'weird' is a bit of a stretch unless you know something you haven't mentioned.

I can see why you want to go, it'd be hard not to be very nosey and intrigued by this woman, but your son would need to ask this lady if it is ok if you tag along. To turn up uninvited is really rude and a bit over the top parenting.

Plus, you might jeopardise his millions! 😆

When I’m in my 60s or 70s I hope I have some polite young men to accompany me to lunch.

*Completely missing the point of the thread and turning it into my personal daydream.

Ooh this sounds like the rather delicious premise of a Sunday evening costume drama. I'm sure Charles Dickens has written a story about this.

I say pip pip and what larks, let the lad go and let him be the hero of his own life.

As I suspected there was a back story. No I wouldn’t go but I would be clear with your dc that he shouldn’t agree to anything on the trip. Maybe the lady may have no negative issues at all but wanted to meet the beneficiaries of the will to talk about her DP? He won’t know until he meets her.

Well after the lunch he will be able to tell you. Please report back.

Let him go, in both senses. It's one of the ways he'll learn how to be an adult.

This is such a weird drip feed if you wanted any useful feedback.

OP: my 18 yr old son is meeting an elderly women in London for lunch

OP later: Oh it's to discuss a Will for sure

OP later ? : Son is also sole beneficiary to the Cyril Sneer dynasty. He hates racoons.

I have a similar age ASD DC and, in the circumstances you describe, I absolutely would go.

I know how easy it could be for them to be made to feel guilty/tug at their heart strings OR how easily they could be wounded if they were to throw a load of ‘you don’t deserve it/it should be mine’ accusations at them.

Of course it could all be a perfectly innocent ‘just want to meet you’ meeting, but I would go.

Given your update, I would probably go along if DS wanted me to. (One of them would, the other not so much).
Actually, I like the suggestion of being close by if needed)

It wouldn’t be unreasonable at all for him to ask her what she wants to talk about. I think it’s odd to ask someone you don’t know to meet up with you without saying what it’s for.

Given the circumstances I would probably go for a coffee round the corner and get him to text you if she turns on the waterworks or starts to try and turn the conversation to what she might be entitled to.

My thoughts too. Don't go with him but go somewhere you're only a few minutes away if he needs you rather than half an hour.