I think you should get the
CityPass since you get a chance to experience everything. For Universal, I went a lot when I was a kid and loved it, but a lot of the stuff that I loved is gone and I personally don't see a whole bunch of appealing thing for kids other than the Nickelodeon Blast Zone (or whatever it's called) and Shrek 4D (I like seeing that). Ppl who do have kids say that their kids loved Universal, so I have no clue about that. But there's lots of other cool stuff like the tram and the shows and the Simpsons Ride, but I don't know if your 5 yr olds are tall enough.
I would definately do SW & AP for 1 day each since you can see the majority or all of the parks in a day. I think that your kids would like them, I mean who doesn't love animals? Just be prepared to bring towels or extra clothes if they plan to get wet. If you plan on seeing all of the shows, I'd base your day around them. If the kids get hungry, just bring a snack or you can buy them as the ppl walk buy w/out getting out of your seat. Don't forget that rides and exhibits are open 'til closing, so you don't have to worry about seeing everything when you first get there. If you want something special to add to your day, there are tours or special dining experiences like Dine w/ Shamu (my fave! and you get a reserved spot for the evening Shamu show). And don't forget to bring a nice pair of walking shoes for the AP. Since the weather down here is crazy, it's hard to figure out if it's gonna be hot or cold during March, but when it gets hot, it gets hot! So bring some water! I don't know if you've gotten to experience the new tram ride at the AP, but just in case, it's shorter, you get to be closer to the animals, and there's a small fee. I'm not sure if there's anything special w/ the City Pass for the tram though, but I still think it's fun.
HTH!