Really, not much at all. Disney kinda hides the Halloween stuff until it's time for the MNSSHP. Maybe some topiaries are decorated. See some pumpkins and corn stalk type landscaping but not much at all. Only the MNSSHP gets MK tricked up for Halloween.
Other than some landscaping, you won't notice much at all the parks.
If your kids are doing ok in school I'm a big supporter of pulling them out for a couple days. Much more memorable, educational, cost effective, etc. You won't ever have that birthday again with the kids, make it super special if you can.
Steve-"I'm Grumpy because you're Dopey"
90-Treehouse(1st Anni), 93-Clubhouse Villa(DD2), 96-Hotel Plaza(DD5&2), 99-CR(DD7&5), 01-OKW(expecting DS), 03-POR (luv the trundle), 04-AKL, 06-ASMo(DW 40th, DD2), 07-DLRP/POP, 08-Y&BC/POP/DLRP, 09-ASMusic/Cruise, 10-ASSp/Pop, 11-POR/Cruise