I'd plant it in a well drained potting medium as soon as possible. I assure you that all of those rootlets will break away no matter what you do. Roots formed in water are quite different than those that the plant will get busy making once planted in a solid medium. You can trim the roots before potting up. Don't put into a container that is overly large.

cool! it's actually a labor of love because if I can make this rooting take, then I'll have a tree that was not only "effectively" born at the same time as my son (wifey is 39.5 weeks pregnant) but also will be a cutting from her floral arrangement from her baby shower.

How cool would that be?

Figure it won't be outdoor hardy until at least next year but then again, neither will my own little sprout. ;-p