Give your babies individual names, it would be cute to have matching names when they were younger, but as teenagers, they'd hate it.
I think
Gracie,
Fiona and
Gwendolyn go really well together, if the third baby is a boy i like
Jude,
Thomas or
David.
My favorite combinations would be:
Gracie,
Fiona and
Gwendolyn for all girls, or
Gracie,
Gwendolyn and
Jude if the third baby is a boy.
Good luck! x