Cabanas has a ridiculous variety of options available on that first day's lunch, including adult and kid options. We have hit Cabanas both times (Dream and Fantasy) and been very happy. Yes, everyone seems to have a carry-on bag, but we had a party of nine and did not feel like we had much trouble with finding tables, putting bags to the side, getting food, etc.
Cabanas is a bit more casual than EG (or any of the MDRs), so you don't feel quite as conspicuous coming and going if someone in your party wants to head out into the ship to confirm (or adjust or book) some port adventure, spa and Palo/Remy reservations. If I'm in one of the MDRs, I'm less likely to want to wander in and out....but if you're needing to do any of these things, it's best to do them immediately upon boarding. We had four adults and five kids, so the two ladies left to handle these things and were back with the rest of us within 15 minutes or so.