19'x12' - 3-room tent with LED lighting system and fan $149.99 (Coleman) (we got this one - set it up once, very tall, and pretty big, but with 5 people, mattresses, sleeping bags and stuff, it'll be just big enough)
This large three room dome tent is easy and quick to set up and provides plenty of interior volume and floor space with three twin track doors. This Wolf Mt. family camping tent also highlights a bath tub floor to help keep things dry.
Large Camping Tent 14 Person With 4 Rooms Separate Exit Outdoor Blue Hiking Fish