If it were me, I would go to CRT (and BBB) on the last day of the trip. And here is why:
1. From what I have heard, the BBB hairstyle bun thingy that they do lasts a few days because of all of the gel and spray and stuff. So, your daughter gets to look like a princess for the last day of her trip PLUS during her return home. It will be like making the Disney magic last just that much longer for her. Not sure what they do at the PL, but I am guessing the same extra bit of Disney magic will be extended for your son by going so late in the trip as well.
2. If it is your family's first time at CRT it is probably going to be one of the highlights of the trip, and I am a firm believer in leaving some of the best things for last.
3. CRT is the kind of restaurant where the meal can take quite a bit of time. I'd rather spend that kind of time at a meal during the tail end of a trip when most of the attractions have already been visited and the tired feet have kicked in. It could be a nice, leisurely (albeit loud and lively) way to end your vacation.
Hope that helps!