Thought I'd mention this, as I brought it up recently at a local support group and everyone went 'corr, wish I'd known about that when the kids were younger'.
Neilson holidays offers 1-1 nanny service for any SN kids who attend their kids clubs at no extra cost. So, this kind of holiday isn't the cheapest (typically £500 per person per week). Pretty much everything (such as kids clubs) are included. Also they do last minute discounts.
We went last year for a week, prior to DS1s diagnosis and explained he had some social communication difficulties and he got a lovely 1-1 nanny. This year we're going ahead. 1-1 nanny's been arranged, forms filled giving details of his difficulties etc... Last year both our boys had a wonderful time, so here we go again. Hooray. It was so lovely to have lots of time with just DH and me, time to just sit about talk when we felt like it (not cram everything into the few free minutes here and there), and chill out.
Anyway, thought I'd pass this on in case there are others who might wish to have this info.