For the firworks, I'm the type to head towards the middle of Main Street. The view is not the best, but it's adequate for seeing Zero fly around the castle -- so cool! It's also nice because you know the view isn't spectacular; it's less stressful worrying about someone taking your space or blocking your view -- more wiggle room. But, I think I'm in the minority when it comes to that.
In all the parties we've gone to, we've never been to a sold-out one, but I'm not too worried about it. I'd rather be at
Disneyland than home, and as long as the weather is nice and we're all healthy and well, it should be fun. Hope you guys have a great time! Just enjoy being there and everything will fall into place.