I was in the same boat as you. My three best friends did everything and it was lovely.

I ended up buying them a nice photo frame. However mine wasn't with the intention of them putting a picture of my baby in it. It was just a nice gift to say thanks.

However a mani/pedi voucher would also be ok.

I don't think it matters what you get them. It's just a way of saying thanks.

Fiona