is there a toy gemach in your town? Can you "swap" toys with a friend- that way the toys will be "new" to your kids. I recently went to a second hand store and got a few toys-while it was money it wasn't a fortune. Can you take out new books from the library- a 7 year old might be willing to read to his/her siblings?
In terms of games- hiding go seek, duck duck goose...
Good luck!