Hey OP - I just wanted to put my 2 cents worth in. I think Erica/Erika is a really pretty name and I get the whole changing of your FIL's name from Eric to Grandpa thing but I was going to wonder if, for your DP, it might not be a little bit weird to have his daughters name be so close to his fathers? Would you want to call your baby a name that was very close to your own mother or fathers name?

I'm not saying this is automatically an issue but perhaps is why your DH is unconvinced about Erica.

Having said all of that, and I realise your mum is raising the opposite issue of feeling left out, I truly believe that if you and your DH like a name, you should use it. This is your child, no one elses and EVERYBODY will have an opinion. Like you said, you can't please everyone (and nor should you try!).