For girls I would lean towards Holly because Ava is so common now.
What a about something a little different like

Ayla Grace
Avalie Grace
Avelyn Grace

Holly Grace
Holly Mae (I like this one)

I like Hamish best from your boys names. I think Angus Hamish is a bit of a mouthful too. I think Hamish (or Angus) would go well with a 1 syllable middle name.

Hamish James
Hamish Brae
Hamish Quinn
Hamish Myles

Goodluck deciding.