Hi Kimberly!
The Princess Half is a great race, and the perfect weekend for mother/daughter trips! You guys will have a blast!
The 5K ends in the Epcot parking lot, so you have a lot of options for breakfast. If you plan to have park tickets, you could check out all of the restaurants inside of Epcot. A Princess Breakfast at
Akershus Royal Banquet Hall would be very fitting for your weekend! Or, you could take the monorails over to the Polynesian Resort and have breakfast at
'Ohana. This is my favorite restaurant at Disney World! (tip: if you are booking 'Ohana, be sure to add about an hour travel time on the monorails from the race finish)
If you do plan to go to a park, I think Epcot is my favorite park to do with "adults". The World Showcase Pavilion and the attractions in Future World are some of my favorite things at Disney. Just be sure to walk leisurely and get back to your room early for an early bedtime.
If you don't want to buy park tickets, then I would recommend visiting
Downtown Disney. You don't need a ticket and there is something there for everyone.
The 5K has been on Saturday in the past, with the Half Marathon on Sunday. Just be aware that this schedule is always subject to change. RunDisney has been adding some really fun races and switching up their race weekends this year, so just know that this is also a possibility for Princess Half weekend.
I hope this helps! Please let me know if you have any other questions.