It's workable, however . . .
We did LTT at 6:45 p.m. before
MVMCP in mid-Dec. I tried to get an earlier ADR (suggestion: book LTT as SOON as you possibly can on your MVMCP night!) but couldn't. We still were able to see a parade, the fireworks and do some rides. We would have been able to do more, but my two DS's had a little "incident" in the middle of Main St. and we decided we needed to impose some discipline and cut the party short.
And that brings me to the "however" part - yes, my DS's (9 & 11) like to pick on one another, however, we had been in MK in the a.m. for opening, went back to the hotel at about 3:00 p.m. to "relax" and then headed to the party at about 5:45 p.m. Even with the down time at the hotel, they were tired (which surprised me because they are both very active kids) and I think it was all a little too much for them. If I ever did MVMCP with them again, I would spend the ENTIRE day at the resort relaxing and then head to the party.
If you have kids with you, I would really consider NOT going to AKL in the a.m. I'm not sure where you are staying, but keep in mind the travel time it will take to get back and forth from AKL and MK and the amount of walking you do in AKL - it's a lot. Especially if you stay until the end of the parade at AKL (which is usually around 3 p.m.) It will probably take you an hour to get to your resort (with walking to the buses, waiting for the buses, the ride, etc.) and, with approx. another hour to get to MK and LTT (you should get to your ADR about 15 minutes prior), that only gives you about an hour of rest time!!
If you are with a bunch of sturdy, commando adults (like me!), then go for it. Otherwise, I would seriously reconsider.