I think both names choices you have their are so lovely and meaningful

Have you considered Peta for the girl's first or middle name !!

Isla-Mae Peta Collins
Peta-Mae Isla Collins (love this )
I agree and I really like Peta-Mae Isla Collins!!!!
It sounds so pretty and sweet!

I like Matthew for a boy, but I think your boy's name is perfect because it has such wonderful meaning