What to with a preschooler in Yosemite?

You can bring bikes or rent bikes with kid trailers at Yosemite Lodge. That's a great way to get around the Valley floor and see all the sites. We have a Kelty backpack for our preschooler and he enjoys hiking with us in that.

My kids loved the waterfalls in the valley. Most of them are relatively easy hikes less than half a mile. In the summertime, you can get drenched at some of them (Bridalveil for instance), so bring some raincoats! If you're inclined to take a slightly longer hike of 2 miles, you might want to try Mirror Lake. Mirror Lake in the summer can be a great place for the kids to splash in the water. It also has a small beach to picnic on and a wonderful view of Half Dome. Riding bikes, taking a stroller, or bringing a backpack to carry the kids can be good ways to rest tired little feet.

Splashing and playing in the river were our young kids favorite activities. Favorite spots are Superintendent's Bridge, Housekeeping Bridge (access from Housekeeping camp), and Happy Isles. The Nature Center at Happy Isles is a great place for little people. The trails and bridges in that area are also great fun for exploring. The hikes that you take as a family can definitely be done with the little ones... and there is almost always an ice cream spot near by!
I'd recommend finding some fun activities and crafts to do while camping (I'm not sure if you are camping but these activities can be adjust to meet your situation). Check out resources such as Family Fun magazine or a great book we love called, "Camp Out!"
The shuttle bus is free and can take you to most any destination in the valley. Little ones love riding the bus, and I highly recommend using it. We used an umbrella stroller which folded up easily to get onto the bus and then unfolded to help carry little ones.
Be sure to check out the meadows in the evenings right at sunset. We saw many deer on our evening walks.

Splashing and playing in the river were our young kids favorite activities. Favorite spots are Superintendent's Bridge, Housekeeping Bridge (access from Housekeeping camp), and Happy Isles. The Nature Center at Happy Isles is a great place for little people. The trails and bridges in that area are also great fun for exploring. The hikes that you take as a family can definitely be done with the little ones... and there is almost always an ice cream spot near by!
I'd recommend finding some fun activities and crafts to do while camping (I'm not sure if you are camping but these activities can be adjust to meet your situation). Check out resources such as Family Fun magazine or a great book we love called, "Camp Out!"
The shuttle bus is free and can take you to most any destination in the valley. Little ones love riding the bus, and I highly recommend using it. We used an umbrella stroller which folded up easily to get onto the bus and then unfolded to help carry little ones.
Be sure to check out the meadows in the evenings right at sunset. We saw many deer on our evening walks.