Hoop Dee Doo with a mixed group

[nicolem]

Apologies in advance if this has been asked recently, but I can't find it using the search feature.

My family (me, DH, 3 boys, and my parents) will be staying off-site in early June and we'd like to meet up with my aunt and cousin's family, who will be staying at POR and using the dining plan. We would like to try HDD, but I can't figure out the best way to make the reservations. If I make them, I have to pay in advance for their meals, even though they'll be on the meal plan. I'm not sure what would happen if my aunt or cousin tried to book all of us (since half of us aren't on the dining plan), but they aren't as tech-savvy or as familiar with Disney and they've asked me to handle reservations. If they book their own (using their travel agent) and I book for my family, will it be possible for us to sit together (assuming we arrive and pick up our tickets at the same time and order the same category)? We've never been to HDD and I'm not sure how it's set up.