Last Feb, we took our DNiece (16) with us to WDW. Once or twice she went to the parks on her own using WDW transportation and a couple of times we left her and DD - 3 yrs - in the hotel room. We had our cell phone and she had one, and the regular phone in the room. Worked out great. I think as long as you have communication and some schedule like, "I will call at 2pm" or something like that, it will be fine. I am a real "nervous nelly" but I felt pretty good about her safety while on Disney property and using Disney transportation. Of course, it depends on your comfort level and DD's responsibility but I think she would be fine.