Collect a drawer full of things like farm animals and drawing materials, old greeting cards that you can cut out shapes from and stick onto scrap paper to make pictures, collect bits and bobs that fascinate children - my twin grandsons love mooching through a tin of odd scraps and odd objects and using them in imaginative play. The Mr Tumble (Justin Fletcher - brilliant) DVDs with songs and sketches are fantastic - 2 and 3 year olds love watching them repeatedly and singing and dancing to the songs. My daughter also records programmes on CBeebies like Grandpa in my Pocket, Dora the Explorer and Gigglebiz to watch again. Having something like a garage, dolls house, or similar will keep them occupied.
We play games like 'I went to the shop and I bought.....' and get them to scurry off and pretend to come back with ingredients for a cake, or their tea. My grandsons love pretending to come back with the 'wrong' thing so they make me laugh - it all uses up energy - theirs, that is, not mine! I spy, asking things like 'where can you see.....a squirrel, or a telephone, so they have to search the room to find what you have seen.
Also, don't forget everyone can settle down after lunch for a cuddle on the sofa and afternoon nap, which children that age still need.