The idea of grandparents traveling with grandchildren ("grand-travel") is a "win-win-win". The grandparent(s) get to enjoy the little darlings, perhaps in a way not possible in the hectic days of raising their own children. The grandkids experience a special vacation. And the parents get a breather, and time for themselves.
Single parents face special issues, starting with pricing: how will the vacation be priced, given that rates are usually based on two paying adults? See tips, plus some agencies and resorts that focus on single parent vacations.
All families needs vacations, and it could be argued that those with the daily extra challenges of special-needs kids have a special need for R&R-- yet they may have a harder time finding it. Fortunately there are some choices.
"Family reunions" might refer to a big occasion where the whole gang of extended families get together once in a long while. But another type of family gathering is going on: extended families, often with grandparents, are getting together on cruises, at resorts, at Disney World... and some destinations are trying to make the logistics of "multi-household" travel easier.