I don't know how big your pit is, but our preschoolers love to just slide, roll, & jump into it. We also have a trapeze bar hanging from the ceiling that they use to swing into the pit and a beam that they use to cross it.
You did ask for games and we have a couple that we play.
One is to race across the pit. I don't know the size of your pit, but ours is fairly small, so we do this the long direction. Two kids jump off at the same time and have to try to get out of the pit first.
The other is a pit fight. The kids love to throw and be hit by the foam blocks! You have to be careful with this because as the foam degrades, little pieces can come off and get in their eyes and that hurts!
Older children like to get on the beam and try to knock each other off, but I wouldn't try that with preschoolers!