Well, if he truly just wants to walk into MK, it’s entirely possible if you guys are willing to spend the money on tickets for the atmosphere. MK will likely close to one day ticket holders in the late morning of NYE but should reopen later in the day. So check before you make the effort to go there to buy tix.
We are going to Epcot at about 7pm on NYE and plan on practically no rides. We just want to hit the dance parties and party all night. That said, we will also be going to AK in the morning for a few rides and shows and have our FPs for those.
We are also doing Mk on the 30th with little planning. We will spend the morning in DHS with FPs, take a long nap, then enter MK about 7/8pm (AFTER the early fireworks) to party with the DJs, maybe hit a couple of less popular attractions, and watch the midnight fireworks. After that we plan to hit rides hard until the end of EMH at 2am. I expect most things to be a walk on in the last hour.
Also, I heard refresh works really really well during the holiday season. Lots of ppl there At that time of year don’t know how to maximize FPs so power users have a definite advantage.