Put on some music and let the kids dance/run/move to it. Vary the music so they have to move fast and slow. If you can stand the noise, let them make instruments and play along with the music.
Teach the kids how to somersault and let them spend time somersaulting.
If you have carpeting, get carpet skates for the kids.
Play Simon Says.
My youngest always had to move when he was younger. One day he measured the longest path through the house and figured out how many times he had to walk the path to walk a mile. He would walk a mile or more every time he felt a need for more activity. You could do the same with your kids. Or you could have them hop, skip, crawl, etc. through the longest “straight” path through the house to give them some exercise. Vary what they have to do and keep it fun.
And on days when you can get out:
Let them make igloos in the snow.
Make snowmen, or learn the art of snow sculpting. 🙂
Go sledding.
Have older ones pull younger ones on sleds.
Make snow angels.
Give them spray bottles filled with colored water to “paint” the snow.
Catch snowflakes on dark cloth and look at them with a magnifying glass.
