Hi Melanie!
Thank you for bringing your question to the Disney Parks Moms Panel!
The Star Wars Half Marathon - The Dark Side weekend is so much fun! You guys will love that race.
Basically, the family meeting area is an area close to the finish line where there are large signs posted with letters. Most families will agree to meet close to the sign that corresponds with their last name.
There really isn't any type of supervision for children there. I recommend using
Kids Nite Out. They are an independent company that contracts with Disney to provide childcare on property 24 hours a day, 7 days a week. When my boys were younger and my husband and I both ran, that's who we used. We were always very satisfied with our sitter. Many other Moms Panelists also highly recommend them.
I hope this helps! Please let me know if you have any other questions.