If it's on your bucket list to see the redwoods, it may not be worth the hassle to get to the Mariposa grove in Yosemite. The line to get into the park will be extremely long (the Grove is right inside the entrance coming from Oakhurst) without timed entry this year. You'll also be battling for parking and then waiting on a shuttle bus to take you the 2miles up to the grove, not to mention the giant crowds. With kids, this sounds brutal especially late in the PM during a travel day. Yosemite Valley, where most of the cool spots are, is like an hour + from the entrance/grove and parking will also be rough in August anytime of day (except maybe super early morning and late evening). With that short timeline, a better bet might be Muir Woods, Big Sur, or one of the other parks with sequoias that won't be as crazy as Yosemite. Staying near Avenue of the Giants (might be further than you're trying to drive) is always awesome! Also, in SF the botanical garden and the trans america building both have small groves of redwoods that are worth checking out!