We put in a deck over the summer so that there is a flat place for the toddlers to walk as that was one of the big issues. What I find is I do physical activities in the house with the little ones with balls, tossing bean bags, they push trucks around the house, I have exercise balls I hold them on for bouncing, etc. When they go outside they head straight for the sandbox and just stand there playing. I always have to laugh when people talk about the need for outside time for physical activity - with the little ones it is strictly for the fresh air and the physical happens inside.