To stop bending over backwards to accommodate anxiety

you could reduce the frequency or completely cease seeing him with other people, or if you do, just do what’s best for you personally, eg say you’re unsure of the plan, get cabs or stay over. See him 1:1 and have options for things you can do that day or evening if he cancels.

You've set yourself up by always worrying what works for him. In future tell him your plans and he can go with you or not as he sees fit

I’m also ND (ADHD) and find strict plans too claustrophobic and stifling, if there are too many too far in advance I’ll just forget (yes, even if I write them all down). Yes, you need to plan things like travelling to an airport or making a dinner reservation but a day out with friends can easily be more casual and “go with the flow”. It isn’t an NT vs ND thing.

For times when you want to drink, how would you normally get to and from the venue? Bus? Train? Uber? Just do that.

Food served - give an hour's time frame or 'deffo by 7' kind of answer.

Can you talk to him about how accommodating his anxiety impacts you? There's anxious and there's selfish.

Assuming you’re both adults why are you even having this level of involvement with him? You live you life as you want, and tell him sorry brother, I can’t give you a lift/tell you exact plans as I’m not driving/don’t know the plan/I’m busy that day. If you both end up invited to the same event tell him he can plan his own transport/timings etc in the way that makes him most comfortable but you’ll be doing the same, so you’ll just see him there. Is he getting help? You’re not his mother or his chauffeur!

Planning the day is just good manners.

It really isn’t.

Things change. other people have good ideas. One things leads into something unexpected.

When there’s plans, there’s people who moan about the time, and rush you to the next thing.

What is he doing to manage/deal with this?

Counselling/medication?

I've suffered with severe anxiety issues for years and have had a lot of CBT, therapy, and trying different medications.

If he's an adult he needs to be doing something about it.

And why can't you just stay over somewhere if you want to? Tell him that's happening and he's welcome to either join you or not if that doesn't work for him.

Feel empowered to say you are staying over, and he may do the same or drive himself.

He’s your brother, not your child. Do things without him. Tell him what you’re doing, however you want to do it, including things like not being sure if you’ll stay over or not so can’t drive him home. He can sort his own taxi out.

It isn’t enough to identify the problem and then expect everyone to work around it. He needs to identify the problem and then do something about it.

Of course it’s nice to make sure he can be involved in stuff, but it actually isn’t your job. Say no sometimes, tell him you can’t give anymore detail as the day isn’t planned sometimes. Then do it his way other times for important family occasions or whatever:

How old is your brother? Is he on medication and having counselling?

Planning the day is just good manners. At least as far as my ASD brain is concerned. I don’t know how NT people manage without a schedule.

If you can’t be specific, at least provide a time range. the meal will start sometime between 12-2 so arrive after 3 to be safe.

the rest of it, you just say no. You don’t have to be your brother’s assistant. Make your own plans and don’t wait for him. Tell him you will likely be drinking and he needs to plan a ride of his own. Even if you decide not to have a drink, he then at least is covered.