With your boys' names, I prefer Mackinlay
Drew over
Carson Mackinlay, though I would choose the latter in other circumstances.
Niko,
Emerson and Mackinlay just sounds better to me than
Niko,
Emerson and
Carson, because of the repeated "r" sound as well as "son" component, too similar for my ear. I wouldn't balk at someone else making the choice, though.
I like Mattea;
Matea always looks like it's missing something to me. I pronounce them both as you do, though.