I would make your ressie at whichever kids club is closest to where you would like to eat.
If in the MK area, I would choose the Neverland Club. There is no time limit there (some clubs require you pick up the kids within 4 hours, so be sure to ask), and the meal is included. If at WL then the Cub's Den, also no time limit, but you have to pay extra for the meal. If in the Epcot area, then the Sandcastle Club at the Beach Club Resort. We haven't used it, but have talked to those who run it, and it seems very nice. Don't know if the meal is included, or if there is a time limit, though. And finally, if at AKL then Simba's Club. I believe the meal is included here, as well. Don't know about the time limit.
One word, if you are going to DTD for the evening, plan to leave and catch a bus back to wherever your kids are staying about 1 hour prior to the time the kids club closes. Also, you might want to think about taking a cab from the kids club back to PO-R, as otherwise you will have to transfer at DTD, which can be a nightmare later at night. We always do the cab, and the extra $10 bucks is definitely worth it to eliminate the hassle!