I too love the name Mikaela -- I would personally go with a single syllable middle name:
Good luck to you!!!
I also think single syllable sounds best.
mikaela anne (spelled witho r without an e)
i actually really like the name grace for a middle name too.
Agree with those that said single syllable, whole heartedly!!!! I like Rose. Just a suggestion, is there a significant person you could borrow their name from? My Jillian's middle name is from my sister, her Godmother. It's Marie.