Not a huge deal to be in park. Sat, Epcot is really the only park that will have any runners going through while the park is open. Sun the biggest problem will be getting to places for early morning anything. Be it an ADR for dining, rope drop, whatever, take Disney transport, and allow for extra time due to road closures. For instance, the primary road to the MK/Contemporary becomes a single lane for several hours while runners go that way, so they send 20 cars one direction, wait for them to get through, then send 20 cars in the other direction. Just watch out for runners during park hours, pay attention to any marked paths and CMs as runners may not be able to stop if you jump out in front of them. A sweaty half delusional runner crashing into you in Epcot around mile 25.5 won't end well for either party.