Oh dear.
The status quo is that your DS was born with a foreskin and I do not think that the fact that you have changed your view somewhat gives your DH's choice priority. It is your child's body, and it is hardly surprising that you do not want your tiny baby operated on for something that you do not believe in and is not medically necessary.
Circumcision is not demanded of Muslims religiously in the same way that it is of Jews. It is not in the Koran (though it is mentioned in the Hadiths, as a hygiene thing, not like a sacrifice as it is for Jews) and not all Muslims circumcise - we have extended family members who are uncircumcising muslims - though it is deeply culturally embedded.
Let your DH read this), and I wonder if you could find a liberal Imam who would explain that it isn't a religious necessity?
If your DS grows up choosing to follow Islam he can make his own decision a out what to do with his body.
But in the end, in your shoes, I would just say 'no' - and get it put on his medical notes. Surely your DH is not some kind of maniac who would take his baby child to an unlicensed illegal operator of some kind?? If he is I would see a solicitor straight away and see what your options are.
A decision not to circumcise can be reversed.
A decision to circumcise can not.
I believe you have the moral right to just say No, and keep saying No.