Hi, Christy!
Let me be the first to say "welcome back to Walt Disney World" after two decades! I think you'll find that while a lot has changed, much has also remained the same. You have a fabulous plan to experience
Mickey's Very Merry Christmas Party (MVMCP) with your 2-year-old princess. By the time the first
Mickey's Once Upon a Christmastime Parade has completed its route through the park, your little princess will likely be "done" and ready for bed, but you can still enjoy the rest of the evening -- and maybe even stay in the park right up until the close of MVMCP at midnight!
The person picking up your daughter can absolutely ride the monorail from the Ticket & Transportation Center (the parking lot for Magic Kingdom) to the park entrance. You can meet just outside the security checkpoint which is a short distance from either of the two monorail platforms. You will have no problem re-entering the park with your MVMCP wristbands.
I've included a link to an
interactive map of Magic Kingdom Park which will give you a good idea of the layout of the park entrance and the proximity to transportation, particularly the two monorail platforms. The
Express Monorail runs between Magic Kingdom and the Ticket & Transportation Center
only while the
Resort Monorail makes stops at the three Magic Kingdom-area Resort hotels (Contemporary, Polynesian and Grand Floridian) as well as at the Ticket & Transportation Center.
Be sure to catch the magical snow on Main Street USA with your little princess before she leaves the park for the evening.
Wishing you a holly jolly time as you celebrate the holiday season with Mickey and all his friends!