I have to agree with the top comment on part one.
Its like The Avengers for kids. And that is awesome.
Though Santa reminded me of heavy "That was just expression".
EDIT: Damn, I did NOT like the second trailer.
Jack Frost is too much the usual teenage boy with powers (in this case truly a special snow-flake) that usurps the majority of the movie.
With just the other four it would have been enough. I can already see them following the formula and making 60-70% of the movie about Jack exclusively to focus on the character kids can imagine themselves to be.