We were there a few weeks ago, and parked on Main St at about 8pm for 9:45 fireworks. Off season, but a Saturday night (both SoCal and AP's blocked). We had a stroller and 3 kids, so felt we couldn't just "walk up" to find a spot - we were just too big. The fireworks were delayed, then finally cancelled by 10pm. It seemed to take forever to clear enough people so that we could get the stroller out - we knew by 9 that they were going to cancel everything (flags on the castle were whipping around like crazy), but by that time we were completely locked in by bodies all around. And I now understand why people complain about those who try to "get through" - we got stepped on so many times!! My eldest child had to stand, simply so he wouldn't be trodden upon by tons of people trying to walk over everyone! Perhaps DL should consider keeping open a walkway or something, because I swear I might have gone a little ballistic if we'd gotten stepped on one more time!
Not sure if there is a solution with little ones, though, especially if you will have a stroller or various other space consuming child related paraphenelia.
Sorry - I didn't answer your question - just thought I might shed a little light on how things sometimes go - I didn't understand before....now I do....