Actually, I think it's 54" for Manta. My 8-year-old was just tall enough. Double-check their Web site, but I'm pretty sure (we just got home from our trip on Saturday, still tired, so my memory could be hazy). It was definitely 54" for Kraken, which he was thrilled to ride.
The Manta is AWESOME. Try to get in the front row if you can for an unfettered view. It's fast but so graceful...you soar and flip! And while you're in line, you're viewing a great manta ray aquarium in a nice, cool cave.
You can definitely do a lot if you get there at 11:30. We LOVED Blue Horizons, the dolphin show, and of course Shamu. We saw both Believe and Shamu Rocks. The stunts are similar, but Shamu Rocks is done at night to rock music. If you want to take pics, be sure to go during the day, because the night show is too dark for good pics (and I was using a high-end Canon digital camera, albeit not with a super-fast lens). If you have a video camera, you can shoot the shows as well; they don't have a problem with it.
Shamu Rocks is a great way to end the day; get there at 8:30 if you want to be assured of a good seat, earlier if you want to be in the soak zone. If you are in the upper part of the soak zone, you really won't get wet, but if you are in the lower half, you will TRULY be soaked to the underwear. My boys insisted on the soak zone and we ended up in the front row near the center at 8:30! That water is salty and 52 degrees and not particularly pleasant when the sun's gone down! Bring towels and a change of clothes, and either put them in a locker or secure them in waterproof bags if you go for it. Don't miss the fireworks, either. The viewing spot for them is near Shamu Stadium, and it's a better show than most communities' 4th of July fireworks.
You likely won't be able to catch all of the shows. Check the schedule on their Web site and then see how far apart the show venues are. Shamu Stadium is across the park from Kraken and a good 10-15 minutes. We also sure A'Lure, an indoor show, which had great acrobatics from the Chinese acrobats. The only shows you really need to get there 30 minutes beforehand are Shamu shows.
I have no idea what CS is.