12th Birthday Party Ideas?

By "out of the house" do you mean movies or rollerskating, or do you just mean an outside activity. I always used to take my summer birthday parties to the pool, and I have taken a small group to the movies. If it is just outside, a trip to a park - perhaps even having the whole party there, might be nice. You could do a treasure hunt or a scavenger hunt, do activities that are available in the park - badminton, lawn bowling, soccer, etc.

I am not sure if I am a big fan of having two groups of party-goers, unless she is inviting quite a large group for the main party, and a couple special friends for an extra sleepover. To invite some for the outing, but not for the main party seems ungracious to me.

Birthday cookout, picnic and/or campfire sounds like a fun idea and maybe have a large tent for sleepover if you want to stretch the time. Outdoor games and if no pool, then a water hose will do or water slide and water balloons sounds cool and refreshing on a hot day.

Also, a cooler of ice for lots of cold drinks and ice cream cones or watermelon and sitting in the shade enjoying fun with friends and party foods.