I am not sure why you are wanting to do this without adoption. Step-parent adoption is relatively easy and inexpensive. Further, if something should happen to you, wouldn't you want your husband raising your child? If something happened to your husband, wouldn't you want your child to inherit from him or be compensated for his loss?
As to changing the name, any parent can file a petition in court to have the name of their child legally changed. You could change it to anything you wanted, as long as you have permission from the biological dad (if he is listed on the birth certificate or has court-ordered rights) and the change is not to defraud creditors. For that matter, you could even change his first name, as well as his last. But I strongly recommend that you consider step-parent adoption under the circumstances you describe.