I’m taking my first solo trip this early December. I will be in Orlando for a work conference and will be able to go to the parks in the evening.
I had something similar last December where I stayed for a few days after a conference and went the parks (full days) and more recently in June (just evenings) once the conference started at the Swan and Dolphin.
December was a great time to go. It was my first time at Epcot so the addition of the Christmas stories at the different country pavilions was nice. I definitely recommend doing some of the table service restaurants even if you are solo. I have good memories of Hollywood Brown Derby, Sanaa, Liberty Tree Tavern and Le Cellier and even some of the character meals like Tusker House and Garden Grill with the cast members being great (my one regret is not getting the name of the cast member at Tusker House who stepped in and took some photos of me and the characters for #CastCompliment).
Mickey's Very Merry Christmas Party was also a lot of fun though it made for a very long day (PPO at BOG through to the end of the party with a short break in the middle of the day to dry off after getting caught in a torrential downpour that morning in which I thought "I can't possibly get any wetter than this" at least 3 times... leaning into the initial start of the rain on Splash Mountain, sitting under a canopy spout on Jungle Cruise as it started to get heavier, and then getting caught in a downpour walking by the castle... so, yeah... maybe pack a poncho, though there was less rain in December than in June).
Doing the conference and evenings this past June, I overbooked myself. My wife was able to come down for the Friday to Tuesday morning so we had some full days in the park together (workshop on Sunday so just the evening together in Epcot that day) and then 4 evenings and Saturday morning on my own where I bought tickets for Villains After Hours for the Thursday and HS After Hours for the Friday. With the parks closing a bit earlier in December, I actually had a better experience for the solo part because I wasn't pushing myself to try and get every possible minute of Disney time in the same way. Or I was, but there weren't as many available minutes which provided a better balance. I think I'm trying to say something that involves flowers, slowing down and either smelling or eating said flowers (still thinking about some of those table service meals... cheddar cheese soup and pretzel bread... oh my).
There's a lot of stuff that's just a blur from those two trips, but also some really great moments that stand out from when I was able to slow down a bit and appreciate where I was at. I think I'm just getting to the point where I don't feel like every trip is going to be my last trip, so I'm hoping that I'll start to be a bit better about finding those moments and hoping that you have a chance to find some of your own this December.