If you want to see some very nice quality petroglyphs and dinosaur footprints, head North out of Moab, and then West along UT-279 (Utah 279).
This road more or less parallels the Colorado River, and after several miles you'll pass a historical marker on the river side of the road. Pull over. This is the first of two sets of petroglyphs you'll see. Just a short jaunt down the road, you'll see the next marker, and the next pull out.
There is little through traffic, and it's pretty safe for the kids.
Push further down the road, and you'll find a turnout on the right. Park in the lot by the 'markers' and you can see the dinosaur fossilized footprints up the hill. My son and I hiked up to get a better look.
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