Mariposa Grove of Big Trees of Yosemite National Park.
This is a great introduction to the beauty of Yosemite NP. Different from what is ahead, this is a good starting point. If you plan to visit Mariposa Grove allocate some good portion of the day to walk around, get a feeling of these centuries-old trees.
Even though it is very moderate hiking even with kids (bus tours are available), "tough" hikers can find joy walking these trails as well. Plan It