I can understand your concern about your baby's health. Now I will put the matter of medical facts and will leave the decision to you.
Madam, diabetes is a congenital disorder. It is carried by a recessive gene. Recessive means the one which is subdued, not dominant. The dominant gene is always non diabetic. The very fact your husband is diabetic means he has both the diabetic recessive genes. You are not diabetic. This means that either your both genes are non-diabetic dominant or your one gene is non-diabetic dominant and the other is diabetic recessive.
Woman's egg and man's sperm both contain only one gene from each pair. So when you become pregnant, your baby will have one gene from you and one gene from your husband. Now if you are having both your genes dominant, then your baby will definitely have one dominant and one recessive gene; meaning thereby the baby will not suffer from diabetes but will be a carrier. Your grandchildren carry the risk of diabetes, depending upon the status of babies partner. If you also have one gene recessive, then there is 50 % chance of your baby having diabetes. Now which baby will have it is very difficult to say without the chromosomal/genetic study.
How to find your genetic configuration must be the question now bothering you. That can be done only by chromosomal study which is a very costly test.
Even you do not know whether your son is having diabetes or not. Diabetes of type 2 variety develops late in life.
You have now to decide whether to take the calculated risk or not and err on the safer side.
The decision is to be taken by both of you jointly without any emotional turmoil.
Remember, the total population of diabetics in the world is increasing very fast and all of them are not opting to be childless.
Still if you do not want to have the child suffering from diabetes and are keen on having one more child, you can opt for adapting a child.
The decision is entirely yours.
I wish you best of luck.