I'm an autistic/anxious adult. I'm married and we have no kids.
My main holiday is a week in the same Welsh village, in the same holiday apartment, on the same week every year. There's a beach, chippy, icecream shop, a couple of little shops. We visit the same 3 towns on the train during the week. We've been doing it for 9 years, but it's also a place I went to regularly as a child. I can properly relax for the week because I know what it's going to be like and exactly what to expect. My husband loves this week too, because he can go for long solo walks while I stay home to nap and chill.
I can also manage a weekend in London, I can do one activity a day and eat a hotel picnic from M&S, or get a Macdonalds. We stay in the Paddington area because it's familiar now, so lessens to anxiety.
I last went abroad 12 years ago. Long haul flight on my own. I stayed with my friend and when she was out at work I literally stayed in her flat alone and read and wrote and watched TV. It was lovely 😁 I did my normal things but with an excellent view. I did outings with her, but was very overwhelmed with crowds and being too hot. I haven't messaged to go abroad again, even just booking it seems too complicated, and my husband feels the same.
Maybe try holidays with her, where everythings the same every year?