I give to my godchild and we get from our DCs godparents. At least, in principle - I'm now panicking and realising that actually, we do normally give to the godparents' children but we haven't this year (have had a horrible time in Nov/Dec so have got really behind).
One set have grownup/older children, we give to the parents but we had done for ages before having our own DCs/them being godparents, two sets have their own children and I have not really thought of giving to those children, one I normally give to as it's a vvv old friend but shamefully forgot this year, and one has no children but gives her godchildren a present on an anniversary rather than at Christmas (the DC whose godparent this is will not notice).
So actually, erm, I'm going to need to send a couple of apologetic texts for late presents, I think! In general, yes, if friends/relatives have children we give reciprocally. But occasionally this does not apply.
I'd say that if you have friends/relatives with older DCs then you might have been giving to those DCs for a number of years before your DCs came along, meaning that you might not give them gifts after secondary school/teenage/leaving school, depending on how close you are, but that might mean you have a few years "left over" where your younger DCs get presents.