Suits!

I think the pink tie will be fine. I personally would prefer it over a grey tie if they're wearing a grey suit. Not a fan of full monochromatic when it comes to suiting with accessories. In my opinion, it's too bland and lacks dimension, especially if they two greys are really close. All that grey will just completely overwhelm the outfit.

One thing you can do is, if the girls are doing any alterations where they need to cut material from the dress, try to make a pocket square out of it for each of the guys. If you do go with a pink tie, make sure their pocket square is not pink. Whatever you do, never match the pocket square to the tie.

I think pairing grey suits with these blue dresses will look lovely together

I agree that adding in pink might be too much, unless you're really playing up pink and blue in the rest of your wedding decor. I think going with another blue shade or one of the dresses would work well (for all the ties - trying to match them to each dress would be a nightmare!), or any neutral like a grey or even a silver or cream could also be nice.