Avril,I am sorry for the even later response, school got so busy for me. Just wait until I am in my fifth year!

Ace is probably the best choice. I've always seen him as quite rational, even for his age. Even with if he became busy with work, I'm sure he would leave your younger siblings in better care than Aunt Jade. Let him know that my mother would be quite happy to spend some quality time with her nieces and nephew, especially now that summer is hear. It could be just like my sister last summer at your home, if Ace becomes busy enough.
Best Wishes,
Edgar