As far as child "friendly", most restaurants here are great with kids.... there are tons of kids here and I can only think of a very few restaurants where I would not take them. If it is a very expensive place, then I don't bring the kids. Otherwise, everywhere is welcoming!
As far as a specific recommendation, it would depend on what part of the city you are in.
In Golden Gate park there is a great Children's playground (just keep an eye on them, it is big and has lots of exits)... the butterflys are at the Conservatory of Flowers now, the de Young art museum is there (mught be too young for this though)... if you do go to GGP there are lots of restaurants near 9th and Irving. Park Chow is good and kid friendly.
The Exploratorium is great, and you can walk up to Union Street and eat at any number of places, all very welcoming of kids! I like Left at Albequerque, but there are tons of places on Union, or even on Chestnut. Then you could go down and take a walk on Crissy Field and have a great view of the GG Bridge, hopefully it won't be too foggy!
Are you coming soon? Just remember to check the weather. It is often COLD here! Especially in the summer... layering clothing is KEY!
Enjoy the city! PM me if you have any more questions.