P.W.
OMG I just saw the most amazing thing when we went camping a couple of weeks ago. Unfortunately I don't know the name of the thing, but a group of people in the campground had about 6 babies among them, and one of them had brought this massive plastic fence playpen structure thing, and they put a tarp under it and it was like this daycare for kids at the campground. It was so cool and such a great idea. (My kids are long past that, however.)
So the thing exists, but maybe someone else can tell you what it's called.