And I don't want to have to crate him everytime I need to get something done.
Unfortunately, for now, I agree with our wise Moderators - puppy isn't old enough to be left to run freely with your little ones. Three ways to keep puppy separate from playtime:
1. Can you partition an area for your pup to be in, using baby gates, etc, so he can see the action, but you can do your stuff? It is not harmful for puppies to have some separate time, as long as they aren't lonely and can watch all the goings-on.
2. Put him in his crate now and then - this will help with his crate-training and comfort level in his crate because he can hear people are still around.
3. Use a short leash or length of rope attached to his collar, to keep him "tethered" to you. Tie other end to your beltloop or apron or whatever. This will keep him near enough to you that you can see what's happening, while leaving your hands free. As a bonus - following you around like this helps lay the foundation for leash-training for walks when he is older.
As for the play-biting you mentioned - this is extremely important to train the pup to never ever ever bite, even in play! Make sure you use time-outs on this - isolation from "the group" is used by dogs naturally, so he will easily understand this consequence.
Good luck!!