I'm very confident, for instance, that a Eureka! Equinox 6 won't leak on you. It has a tough "bathtub" floor (no seams touching the ground), polyester fly, very sturdy design. It'll sleep six adults, so maybe the seven of you will fit, and you'll have room to stand. Cost is $300 at Campmor.com right now, which is a pretty good price. Eureka!'s Kahuna is a little larger, although still technically a six-person tent, and its interior room can be divided into two spaces. Cost is $350 (www.eurekatent.com).
A third excellent option is the Sierra Designs Bedouin 8 ($400; www.sierradesigns.com). Now, Sierra Designs has been making tents for expeditions and other extreme uses for yearsit will NOT leak. It has a big vestibule for storing stuff, fabric that's treated to resist mold and mildew, a mesh canopy roof for warm weather, and enough room to sleep eight adults. It's even reasonably light at 24 pounds.
Of course, it's always prudent to spend time setting up a tent to help keep it dry. Try to find slightly high ground to improve drainage in case of rain, and to help improve the longevity of the tent cut a ground cover out of polyethylene sheeting purchased at a hardware store. Cut the groundsheet so it's slightly smaller than the tent floor. It will help protect the floor of the tent from abrasion.
Check out Outside's Gear of the Year winners in the 2005 Buyer's Guide , then get yourself a copy of the issue, on newsstands now!