Claire236, as your DS doesn't have the medical issues DH and DS1 had, and there are no cultural pressures, then I agree with everyone here that there is no need for your DS2 to have a circumcision.
I'm sure if he's old enough when you explain to him what it would have entailed for him to look the same as Daddy and Big Brother, I'll be willing to bet he'll pass up on the 'chance' to go get it done, just to look like the other males in his family.
Circumcised males, if the press are to be believed, less likely to contract AIDS. Guardian article here
According to DH (circumcised, religious purposes) it enhances sexual performance too, helping them to last longer, as well as being easier to keep clean.
I was very wary of having DS done, but as DH was strong in his religious beliefs, we spoke to many of his friends, that were also parents of boys and they all said to do it sooner rather than later. It's felt he can't be raised a muslim if he doesn't have it done.
DS only cried when the anaesthetic was administered, otherwise, he slept as normal, wee-ed as normal and seemed utterly untroubled by it. Whereas we agonised about it, and were worried about what effects it would have on him, he seemed to suffer no ill effects at all.
If I were to have another DS, would we do it again?... hmm, not so sure I would automatically do it. DH is far less religious than he was, so perhaps not. As I've lost the last 3 attempts at DC2, I'm not likely to ever have to take that decision.
With your family circumstances Claire236, I personally wouldn't do it.