Inexpensive Kids Toys? Foam Planes, etc.....

Colored chalk is good if there is a place to write on. Large diameter pieces are good for small hands. Silly string is fun but can be messy. That may be not appropriate for the smaller boys. Jigsaw puzzles are good for indoor play. There are ones made for different ages. When our boys were a little older we used the dinette table in our TT for a large puzzle. We always ate outside so the puzzle could stay in one place until it was finished. We never hooked up the TV so they did different activities than they did at home. A simple ball toss at a board with a hole or holes makes a game for all ages.