Hi Nicole! That is so sweet that your parents want to be there!
What time they need to be over there will depend on what part of the race they want to see you. A great viewing spot is on Main Street U.S.A. in the Magic Kingdom. Spectators can enter there beginning at 5:30 a.m. (no ticket is required). You will be coming through there around mile 5, so you would need to consider your pace and starting corral to determine when you would be coming through. To get there, your parents would need to take the monorails from Epcot to Magic Kingdom. It's an easy route, but can be long depending on crowds, and they would have to change monorails at the Ticket and Transportation Center.
If they just wanted to see you at the finish line, they could get there much later. The bus from host resorts would take them to the Epcot parking lot, where the finish line is.
They should definitely check out the
chEAR squad packages. You can find them on the website under the tab "SPECTATORS".
The chEAR squad offers different levels of packages. The Plantinum package would offer them premium seats at the finish line (and in front of the castle at Magic Kingdom). But the biggest benefit is the use of the Race Retreat tent at the finish area. There are sofas, chairs, a hot food buffet, drinks, restrooms, television screens with race footage, character meeting areas, etc. They could hang out in the comfort of the tent while waiting for you to get to the finish line. Then the chEAR squad will have reserved seats at the finish line.
Please let me know if you have any other questions!!