A 2 yo can get overwhelmed easily... I have one.
Bring a few books(they can't read so they finish them fast!), bring a coloring book & colors/or Color Wonder by Crayola (they make them in Disney characters, visit the Crayola aisle at Target/
WalMart)
.....I bring snacks in case he won't eat what is available & gets hungry later (cereal bars & raisins work for us).
Stopping in the middle for naps may be necessary or at least wind down time. You can't expect a 2 yo to stand in line after line with no down time.
Extra pullups/diapers/underwear - potty trained or not, accidents can happen. LOTS of wipes! These work for poo, dirt, messy food fingers .... wipes are great for everything, even removing makeup.
Even if they are done with the stroller, they may welcome one after walking a long time. My son hates his, but he always is ok with it when he gets tired (like trick or treating tonight).
Don't push the characters, they are big & can be scary. Looking at them from afar is sometimes good enough, depending on the child.
Be aware of rides where there is a lot of screaming, this can scare the little ones.
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I tried to think of every 2 yo tidbit I could think of, hope those tips help.