I don't really have any tips for the fireworks.
At DisneySea, an alternative viewing location for the fireworks might be on the deck of the cruise liner. Otherwise, I think the "central" viewing areas of the castle and the harbour would work best. I've been reading about obscene crowd levels at Disneyland LA as I'm planning a trip there later this year, but I don't think it's ever that ... chaotic in Tokyo. It may be crowded, but the people are incredible polite. For example, for the Electric Night Time Parade, the first three to four "rows" of people sat on the ground so that the people behind could get a good view. And the ground was cold and wet due to the rain, yet they still sacrificed their warmth and comfort for the benefit of others!
At DisneySea, an alternative viewing location for the fireworks might be on the deck of the cruise liner. Otherwise, I think the "central" viewing areas of the castle and the harbour would work best. I've been reading about obscene crowd levels at Disneyland LA as I'm planning a trip there later this year, but I don't think it's ever that ... chaotic in Tokyo. It may be crowded, but the people are incredible polite. For example, for the Electric Night Time Parade, the first three to four "rows" of people sat on the ground so that the people behind could get a good view. And the ground was cold and wet due to the rain, yet they still sacrificed their warmth and comfort for the benefit of others!