Thanks for the input everyone. I decided to go with the 63 for now. My older daughter, who is the better skier and skiis more often, only weighs 95lbs. As I mentioned, I have a v-drive so I need to get her up to 28-30mph to make the wake manageable otherwise it's just a wall. My thought is that I want her to sink a little bit so she wants to go faster. Figured she'd be riding so high on a 65 that she would be comfortable in the low to mid 20's and the wake is just too big to cut hard at that speed. We will see how it goes. I'm just happy both my kids are slalom skiing.
I think I got a good deal on SIA... $199 for a new 63" 2018 Omni. Now for the boots. Planning to go with Freemax front boot and RTP. I was considering going with a double boot right off the bat but figured with new ski I will go with the RTP for now because that is what they are used to and once they get comfortable on the new ski buy a new boot for the back.