I am open to whatever everyone thinks is a good idea.
A concern that I have with having the wish tonight, is that if the rainbowfaces were to enter the valley now and offer Chomper's wish then that would mean that the other children would not be present to witness the event, as the other children have already left with their parents or grandparents. If they all made a wish the night before, then they could assume that the wish turned them into sharpteeth and thus have enough foresight to meet up with the other "changed" members. But if they were not present (except for chomper, of course) then they would have absolutely no context for why they have been changed. Of course, if they all end up sleepwalking to a common destination (which I seem to remember us talking about earlier, but I am not certain if we agreed to anything or not) then that would resolve that difficulty. Another way to resolve that difficulty, I suppose, is to have each of the gang individually decide to seek out Chomper after the change. This would be a reasonable decision by each of them, in that if one suddenly changed into a sharptooth species it would be logical to seek out the only other sharptooth in the valley for assistance.