I have a similar situation. My husband and I are the god parents to 1 of my sister’s 2 kids, and I have two different cousins where we are the god parents to one of the two siblings. In the past I too felt uncomfortable when it came to gift giving. Here is how I resolved it – and it was different for each situation.
1.My sister’s kid. We exchange gifts at xmas and b-days between her kids and mine. Both of her kids get an equally valued gift and then I buy the godchild an extra gift that is religion oriented – likes books, jewelry, etc.
2.With one of the cousins I knew the other child’s god mother flaked shortly after being named the god mother and the godfather was a bachelor (and not the thoughtful kind). So I felt really uncomfortable giving the one child a gift knowing that the other child’s god parents were not that involved in their lives. So I called the cousin and said to her candidly that it made me uncomfortable and asked whether the other child was upset. She said he never even noticed and assured me that I didn’t need to give him a gift. I still felt bad so now I send the god child a religious oriented gift of a decent value (most recently – cross earrings). And then I send the other child a small gift on his b-day of a lesser value.
3.With the other cousin – I knew the other child’s god parents were active in the child’s life -- so I just buy for the god child. I sign the cards – love your godparents so it is obvious that it is a gift based on the fact that we are the godparents. Again, I try to buy a religious gift – but he is still young – so sometimes he gets toys ;-) (The only exception is if the non god child actually has a b-day party that we are invited to and we actually attend – then I get that child a present).
Given that – I would suggest that if he continues to give to one child only, he sign the card from himself as the god father. Like, “love your godfather Uncle Bob” so it is clear that it is from him as the “godfather”. You might also consider getting religious oriented gifts – but truthfully that takes effort and sometimes the kids prefer cash. Mardells is a good place to go for that type of stuff.
I personally don’t think you should have to get both kids a gift – especially if they are not giving your kids gifts. But, do remember that the sins of the parents are not the sins of the child – so it really isn’t the kids fault that they do not send your kids a gift. And since you have been giving them both gifts all along it may be strange to the one child to suddenly not receive one anymore. You didn’t say how old they were – so if they are still young then they probably won’t even notice. Especially if you have always given them gifts at b-day parties.
I do think it is fairly customary for the god parent to do something special for the child. If you don’t want to give either one of them a b-day gift, don’t. Then come up with some other tradition. Like have him send her a special present on x-mas or Easter (or some other holiday) so it truly does revolve around the religious aspect.
Hope this helps.