Hi Jeanette!
Thank you for bringing your question to the Disney Parks Moms Panel!
That's exciting that your boyfriend's seven year-old gets to come along to
Super Heroes Half Marathon Weekend! I'm sure it will be a great trip for all.
The first thing I would do is call the resort where you're staying and ask for their recommendations. They can probably give you a list of sitters that are frequently used.
Two other companies that I have found in my research are:
1. Fullerton Childcare Agency
2. Sitters Unlimited
You can find them in a Google search. Keep in mind that these are not Disney owned and operated, but outside companies that Guests often use. Your resort may have some more ideas for you.
I hope this helps! Please let me know if you have any other questions.