Nooo I think they are perfect names together.
They are of the same genre and match so nicely.
I think "Liv" and Lucy has lovely alliteration.
And Lucy may get shortened to "Luce", so "Livvy and Luce" also works with rhythm and alliteration.
We have an Olivia, and currently due with 3rd girl who I would LOVE to call Lucy.... unfortunately hubbie had a dog called Lucy so has ruled it out. Annoying!
Good luck and great choices.
Olivia and Lucy are really popular and would likely be not the only one in her class with that name.
I like Olivia and Lucy together but do not like Livy and Lucy. That is a little to close for me. But if it does not bother you and your partner then go for it. Or maybe use the nn Olive instead of Liv/Livy. Olive and Lucy sound adorable. As for the name I can picture it on a baby, little girl and adult. I think it ages very well.
Olivia and Lucy are lovely together. I wouldn't worry about the similarity of names unless Olivia is always called Livy.
I agree with some of the others--Olivia and Lucy are fine (quite cute, in fact), but Livy and Lucy are probably too close. Maybe Livy and Lou/Livy and Lulu? I think if they weren't always Livy and Lucy, it would help.