Just remember if you do 2 (or even 3) separate ADRs to get everyone reserved at the same restaurant, you'll need multiple people to be the lead guest on the dining reservations. One person can't make multiple dining reservations at the same time. We had a similar situation last year, had 2 ADRs for most of our nights, then got to the restaurant a little early to check-in and request that we be seated together or very close together (you have to ask at the restaurant - calling Disney dining won't help). All but one of the restaurants (Beaches N Cream) had us sitting together at the same table - they really do try. But I will say 13 will be a challenging number!! I absolutely agree with Boma - we've had as many as 21 together there! Plus it's an awesome place for a family dinner. Good luck - hope you have many meals together!