I would also like to expand a little on the pool party idea. Maybe it can be called BBQ or backyard party. Sims don't have to just swim but they can hang out in the yard and do all outside activities. Some of my Sims have great yards and I wish they were used more.
Whenever I throw parties Sims tend to watch tv, eat at the indoor table or dance to the stereo. I would like for Sims to hang outdoors, sit on the cool outdoor furniture and drink the pitcher of sweet tea. Sometimes I place the food and stereo outside so flock there...lol Many times they grab the plate of food and drag it to the living room in front of the television.