I guess if I can take an alternative track, if it were a religion different to mine, I would be concerned, because I would consider mine to be true, so I do understand that an atheist, who believes there is no God, would find making promises to such a God, strange and undesirable. The children themselves do not make a promise in infant baptism. So his children would not be making any promises to God. The adults make promises.
And the role of a God parent is not really massively onerous.
Our children's God parents have:
prayed for them
looked after them
bought them gifts
sent them cards
and most were there at the dedication
The plan for us is that when they are older they will have adult,s we and they, know who share our faith and if they wish to speak to adults they can. But they may speak to any other adults once they are adults and the children of these people (about 14 in total, so far) are also family friends.
It is a kind of extended network of friends.
With the exception of the first one above I am not sure that there are any other items that all God parents have done. One did not even make it to the service of dedication - due to ill health.
I guess I am saying this because I don't think God parents in general will have a massive educational influence in their God children's lives and my sister is in our will to care for the kids if we both die, so God parents won't 'take' over.