What do you mean by spend the day? Shop? Hang out in your room? Lounge in the lobby? Eat at the restaurants? Go swimming? See pool hopping thread on that last one, although, depending upon your resort you might be able to get permission from Guest Services for them to go swimming with you. For the non-swimming ideas, I think it's all good, although they will probably have to pay for parking? Not sure about that, we've never had a car at WDW.
Kungaloosh!
Mort.