OP what are his special interests? Could you plan a holiday around that?
I would recommend solo holidays! I used to do that a lot before children but can’t now sadly because I’m a lone parent.
Both of my two have ASD (as do I) but they love holidays (as do I!). It just takes careful planning. Taxi to airport and then special assistance so that there is no queuing/ noise and time in crowds of people is minimised. Both use loops in the airport to reduce noise further and we always go outside of school holidays when it’s less busy.
We always go for at least two weeks because it takes them several days to settle into being somewhere new and they spend several days sad about the holiday ending/ worrying about the journey home so if going for a week we’d only have a day or two there truly relaxed!
Always a taxi after the airport to go to the hotel and then straight to the hotel room for quiet time to readjust and recover from the journey.
We do AI holidays which I’d never done prior to kids. That means I don’t have to worry about wasted food if they dislike something. No buffets though: too busy and noisy and overwhelming: I prebook the á la carte restaurants for the same time every day so we can settle into a routine, although sometimes we cancel and get room service and do a movie night in the bedroom.
They are happiest being on the beach or in the pool all day. For kids with ASD all of normal life is about meeting other people’s demands and schedules to their own detriment so holidays should be respite from this with no obligations. Being in a hotel means they can go to pool/ beach and in a few mins be back in their quiet space in the hotel room for a break, then go back. It also means no hassle about food shopping or cleaning etc.
Going outside of school holidays means pools/ beaches are much quieter so not overwhelmed by people and noise. Having a swim up pool also worked well in case one wants to rest and one swim (younger than yours so can’t leave either alone).
I will usually plan one or two trips out but in the middle of the holiday and flexible on day, and to well-researched places where we can go for a just a few hours and come back if we want. Usually hire a car from hotel or get taxis depending on distance: no coach trips or things like that which would involve time pressures and other people. The main focus really is on relaxing from all of the demands of daily life and spending time with each other but also acknowledging that each of us needs space and quiet breaks in the day.
I ensure I run them through exactly what will happen on journeys etc step by step before we go and show them photos of what the hotel and rooms etc will look like beforehand so it doesn’t feel quite so alien when they arrive. Go through menus of the various restaurants at the hotel with them in advance so they can plan which foods they would like to try. Make sure it’s a hotel with really comfortable beds, choice of pillows and duvets (none of this awful sheets instead of duvets business!!) and take a lot of luggage so they can bring things they need for familiarity from home.
It is expensive doing it all in this way but it’s pointless and not relaxing otherwise. I’d love to be able to take them on 3 or 4 cheaper breaks per year instead of £££ on something that works but ultimately I want to ensure we have happy holiday memories and enjoy the time we are away, and we do by doing it like this (including me) and all look forward to it so much, crippling as it is financially to get somewhere decent. IKOS in particular have been brilliant at accommodating my children’s needs with kind and understanding staff who don’t complain or eye roll about getting them the right pillows or facilitating booking appropriate rooms or bringing breakfast as room service, making adjustments to their meals etc etc. It is yet another way that having access to normal experiences in a manageable way is more expensive for autistic people, whereas in other circumstances we could book a cheap apartment near a beach for a fraction of the cost and it’d be fine. DS may think he wants to do X and Y but you know his limitations so you may have to be inventive about finding ways to incorporate some of the things he requests without it becoming overwhelming. Theme parks several times in one holiday, for example, sounds like a LOT given such places are full of people, queues, noise, lights?
Going on the overnight ferry to France and driving to a hotel also works, if you get a nice cabin so again there is somewhere to retreat to that is quiet and peaceful.
I really want to take them both on safari but I know that will be far more challenging logistically to do in a way that works for them, with enough downtime in between trips out etc. Would certainly need a decent length beach trip afterwards for us all to recover and rest!
I hope you find a way of doing it that works for you because happy holiday memories can be such a precious thing for all of you. And definitely take a holiday on your own if you’re in a position to do that with a DH to care for him! No chance of that here so my advice is to take that opportunity!! Then you can put fewer expectations on any holiday that you take with DS as you’ll have been able to do what you want when you go away alone.