How old are the kids? You might be better off with 4 coach seats rather than business. If you can get the 'couples' style seats then 2 people could sit right together, but the other seats have large dividers between them which wouldn't really work for a child. The 'couples' seats are every other row down the middle section. Luckily there are plenty of business seats on the A380 and it looks like you wouldn't have an issue getting 2 sets of those seats (on Alitalia, they are taken right away).
Looks like plenty of space available in Y, and you could have a whole middle section of 4 seats together for convenience. Also 4 seats on PVG-LAX on MU for a few days that week, as well as PVG-SFO.