I said I would then changed my mind

Please tell me if Im being rude! Im ex-military and my husbands still active duty. I was very depressed at our last base its taken some adjustment to get used to being a "military spouse" instead of being dual military. I dont go out very often because Im in school full time and always doing homework at night and on weekends. Last year I went to the holiday party and had so much fun. But this this year we thought he would be gone on tdy so I told a friend that Id watch her 2yo overnight so she could go to the party and stay overnight at a hotel with her husband. Well, then we found out that my husbands coming home before the holiday party so I really wanna go. This is right after finals too so I would love to go out. I told her that now Im going so I cant watch him. Last year we had even more fun staying out late after the party than the party itself. Im thinking of telling her that she should have the childcare take him during the party, then after, Ill just take him home with me and she can go to the hotel with her husband while everyone else goes out without me. Im not sure what to do. I told her that Im going, but today sshe texted me today asking if I know anyone who can watch him. So I feel like an asshole.