Hiya Holly, and a warm welcome to planDisney! Thank you for visiting us with your question today.
I love your plan of purchasing a 4-day Disney theme parks ticket. I'm not sure which parks you plan to spend time in, but it's pretty wonderful to get to experience them ALL! When I'm planning out my park days in a situation like that, I find it helpful to reference the
Disney Parks Operating Calendar to check park hours, events, parade, and fireworks times. You should start to see those details for your late December dates a couple of months before arrival.
The nice thing about purchasing
dated Disney park tickets, is they give you a little wiggle room on the dates you can use them. So if you purchase those 4-day, one park tickets with a starting date of 12/31, it looks like you could use them any days up through 1/6 (a total span of 7 days). You're correct, New Years will likely be pretty busy. If the park reached capacity on a certain day, you may have to wait and use your park ticket another day in the week.
While prices do vary by date, there is no price surging with Disney park tickets. Occasionally Disney releases an 'across the board' ticket price increase, but you won't see those tickets gradually increase in cost as your dates get closer. I think you would be perfectly safe waiting until August to purchase your tickets.
I hope this helps! And please send me another
message at planDisney if I can offer any park or Disney dining recommendations for your trip.
Sending pixie dust,
Tami