BBS - if your ds does need a medical cicumcision it will be done on the NHS, in an operating theatre and under a general anaesthetic for a genuine medical reason. In that case, it's not a cosmetic procedure, it's a medical necessity (hence the need for referrals, diagnosis and so on).
My cousin had a cicumcision at 10 for this reason.
Personally I wouldn't say that he is deformed/had been mutilated. His op was necessary in order for him to have a functioning penis (sexually - without pain).
Similarly, sometimes girls have a medical problem where the vaginal opening is fused, and sometimes it is necessary to open this in an operation. This again isn't mutilation - it's a necessary medical procedure.
Having the cicumcision done "because it's cleaner" "because there's less risk of STD's" "because his father had it done" is not an acceptable reason in my opinion. And none of these apply to your ds. Hope all goes well with your ds