We used to go for a week every summer with extended family (up to around 2010). It got impossible (well, nearly) to get multiple sites together so we moved the annual trip to another location.
Personally Yosemite is my favorite, so I still get my fam up there every year. The last few it's been in February. No reservations required, no crowds, and an entirely different kind of beautiful than in the summer.
It does require a certain flexibility though, if there's a storm coming I wouldn't do it. We are generally free most weekends in Feb/March, so we keep an eye on the weather and head up if it looks like it's going to be a good one.