San Francisco for 1 Day with young Grandkids.. Suggestions?

1 day's not a lot of time to spend in San Francisco.

Here's a link for things to do Things-To-Do-In-San-Francisco-With-Kids
The 25 Best Family Friendly Activities & Attractions in SF
San Francisco Maritime Museum
Exploratorium
SF Fun cheap
SF Chronicle - Things to do

Keep in mind the summer in San Francisco can be quite cold, windy and foggy. Dress in layers. The kids will be happier if they're not turning blue.

Now over the Golden Gate is Bay Area Discovery Museum the kids could spend the whole day there.

Just a few things off the top of my head. If you want more ping me.