Congrats OP!
Ok, to narrow your list down, first of all I'd scrap all the names with a heavy S sound - as previous posters have said it doesn't really work with your surname. So lose Frances, Beatrice, Grace, Alice, Elise, Eloise, Esther, Estelle, Ursula.
Then personally I'd bin all the Eva/Ava/Evie names. You have some much more interesting names on your list and quite frankly they are this decades Sarah/Claire.
So lose Ava, Evelyn, Eva and Evangeline.
Vivienne Ross is an actress so I'd lose that too.
Nicole Ross doesn't really flow well so I'd lose that too. Jennifer Ross is also hard to say.
This leaves you: Helena, Delilah, Alina, Alana, Georgia, Elaina, Marianne, Caitlin, Lorna, Margot, Eleni, Lucinda and Marielle.
For your boys, I agree that Isaac Ross doesn't work and would scrap Francis Ross because of the S sound.
I'm not a fan of alliteration so personally I'd scrap Robert, Ryan, Ronan and Reuben.
Overall I'd go for Lorna Marielle Ross for a girl and Dominic Aidan Ross for your boy. Beautiful names!