I want to take my whole family backpacking next summer in Yosemite. I wanted some advice:

1) Does Yosemite have a limit on number of hikers who can travel/camp together. I have 7 kids so it would be 9 people total. Last summer when I backpacked Isle Royale in Michigan (with Boy Scout Troop) they were adamant about not allowing any large groups. But I was also at Yosemite last summer and thought I saw some larger groups, so please confirm that I could have a group of up to 12 people in one group (may pick up a few cousins)

2) Last summer my wife & I hiked to Young lakes, it was awesome. I am thinking of doing that with all the kids. We are casual backpackers, so we went out there in one day, spent time just exploring the lakes on second day, then hiked back on third day. If memory serve it was approx 8 miles out and 8 miles back??? In a larger group with small kids I may want to take 2 days to get back to the lakes (making the leave day no-stress, with preps in morning, and not having the pressure of getting 8 miles in the first day.) There was a great meadow with a (dried up then) creek through it about half way, does anyone know if that is over 4 miles from the trailhead so we could legally camp there?

3) Any other suggestions of pretty easy 3 to 4 day hikes for a group with younger kids?

You should be ok:

Group size is limited to 15 people or fewer, eight people maximum for any cross country hiking more than one-quarter mile from any trail.

You'll need to reserve your permit and the reservation quota for that trailhead is 12.

and make sure you get bear canisters! i believe you can even rent them fairly cheap from Yosemite.

Its actually less than six miles back to Lower Young Lake. You should be able to easily make it there with plenty of daylight left even if you leave around noontime.

(In the terrain that you will be going through, I typically expect to average 2 miles per hour with a full pack; that is actual hiking time and does not include rest periods. If any of your children are much less than ten years old, I would suggest that they just carry daypacks with their extra clothes and maybe a little food.)

The meadow that you are thinking of is along the trail that passes Dog Lake. The creek that runs through it is Delaney Creek. The meadow is less than two miles from the trailhead.

Further up the trail, you cross Dingley Creek. This is around the four mile mark so you should be OK setting up camp there if somebody is getting tired. At any rate, when you apply for the Wilderness Permit, tell them that you expect to be at Young Lakes that night.

Because of the elevation, no campfires are permitted at Young Lakes.

I would suggest that you make your hike a loop and take the trail branch that goes down to the Glen Aulin Trail rather than retrace your steps when returning to Tuolumne Meadows.