Since you twins are young the first parade is a must. They might like the characters in their costumes, ones they will recognize like mickey, Daisy, Donald, Minnie. Google Kenny the pirate and he has a map with where the character will be. Having a game plan is usually a must otherwise you wander around and waste time. You are able to enter the park at 4pm with the MNSSHP tickets. We usually enter early and see a few non Halloween characters like Tinkerbell since we are in costume. Then we get an early dinner, no sense wasting party time eating. Some of the treat stops are farther away, maybe pick the trail lines for the girls. Stroller was a must for us, our son fell asleep about 9 and woke up for the 2nd parade and was awake until midnight. Try and get some nap/down time before the party. Maybe pick up some glow in the dark necklaces, we found some with light up pumpkins and ghosts at home dept, Target also has stuff too. Do you have memory makers? There are a few shots where they place ghosts in the picture after the fact. Kenny the Pirate has samples of them and where they usually are taken. We brought a larger bag to dump the candy in since they do provide handfuls.
I assume you have a stroller so bring a grocery store type bag cuz the ones the park provides are not big enough, lol!! TONS of candy. As I recall there was a specific map for MNSSHP to show where the candy was being passed out. When we went the park was so empty that we used a lot of the time to ride rides. I have pics of my daughter and hubby ALONE on Splash Mtn!! My younger daughter was scared of noises so she would NOT watch the fireworks or the parade (such a bummer) but we went to the princess area and they had Cinderella, Snow White and Sleeping Beauty AND their princes!! No one was there for the half hour of fireworks so we stayed in there and got pics and chatted with them all. I love the autographs they wrote like "Snow White has a crush on The Prince", etc. It just made the trip so we didn't mind missing the special fireworks. It just seemed like there was plenty of time to do everything!! Have a blast!