I would recommend a family meet up at the Epcot monorail station if everyone is willing to get going early. For a 2023 half-marathon that I wasn't running, I took the bus to Epcot with the runners to give them a good send-off and then a big group of us were able to hop on the monorail from Epcot to the TTC. We all had to wait a bit at the TTC (cast members had set up a proper queue), but then we were able to take the monorail to the Magic Kingdom. Again, there was a bit of a wait and a huge number of us queued up outside the entrance to the park, but then we were able to enter the park and line the pathway to the castle. It's crowded but the mood is so cheerful and celebratory that it's worth it and cheering all the runners on was so much fun. (I had our runner text us once she ran under the "Magic Kingdom" sign to give us an idea on her timing and so I could tell her where to look for me.) After that I had more than enough time to take the monorails back to TTC/Epcot, get a coffee and snack, and wait to cheer her across the finish line. Good luck on your race!