Harrowby, what Hope says is correct regarding godparents and sponsors, the idea behind them is they will stand in loco parentis in some circumstances. It's quite an important role and in theory godparents - as long as they live - should always be part of children's lives as far as possible. However, it is also important from a religious standpoint, certainly the Catholic Church officially states that they should make sure the kids are up to date on faith matters, though the Catholic Church do allow non-Catholic godparents nowadays and no-one checks.
What floo says is fairly typical though, the role is more often an honorary one. (I was quite surprised, floo, in your case, as your parents were strong churchgoers.) My godparents were relatives of my mother (her sister and husband and her niece), and I can't say they ever had any input at all worth mentioning, she only chose them because she needed to choose someone and didn't mix much outside the family. She was also godmother to one of her niece's children and didn't do anything.
People I've known have not been particularly scrupulous in choosing godparents or sponsors and many godparents feel flattered at being asked, enjoy 'the day' and do nothing worth mentioning.
'Christening' of infants is less common now anyway, most people believe kids should grow up a bit and make up their own minds, but there are other ceremonies.
Non-Christian faiths have similar types of dedication, where godparents are involved, no doubt they take it far more seriously than nominal Christians!
Those of no faith often having 'naming ceremonies' in which other people are asked to stand in loco parentis and make promises.
It's nice to think that kids have someone solid and reliable in their life who is not a parent. I have to say, I would have loved i and could have done with it. I suppose that is the idea behind Scotland's Named Person Scheme but honestly I dislike the idea of the State should being involved.