It depends on your child and how "obsessive" you are about getting things done at
MVMCP.
I would definitely want to be already in the park when the party starts. My main goal is to get to the big ticket rides with the least amount of lines, as this is one of our only times at MK for this trip. We will see the 11 pm parade. But, my DS's are 7 & 10. I have a 6:55 PS at LTT. I plan to try for a 5:30 or so, 60 days out, at CRT (if it's available). If not, I plan to show up at LTT at 5 pm to check in early. Hopefully, we can get in earlier.
LTT is fun, but it really depends on your DD. The food is family style. If she is picky, I would think that a buffet (CM) would be more enjoyable. But, you have to weigh that option with the fact that you will enter the party at starting time with everyone else. If you're just going for the atmosphere, this option is totally fine. But, if you're OCD like me and have X amount of rides planned for the evening, this may not be the best plan.
Perhaps you could consider CRT, if it's available. The children can order from a child's menu. I don't know if you have breakfast planned for here, but dinner is certainly a nice alternative.
You'll have a great time, whatever you choose!