I love when my boyfriend does this. I love every part of him, so what could be more beautiful than your loved one sharing all of himself anywhere he desires? When he ejaculates on my face (as opposed to me swallowing), I see the look of pleasure on his. As a matter of fact, it was I who suggested he do it in the first place; he had never even thought of it.
If it makes you that uncomfortable, you should probably ask your husband why he wants to do it. If the reason is acceptable (i.e. not to humiliate you but to share with you), then perhaps you can re-examine your objections, and then maybe share in this beautiful and often tasty climax.