I agree with the other poster: do the right thing and tell the truth
There is NO possible way to explain a B or AB blood type if both you and you husband is A. If he is not familiar with blood type possibilities, that is your only hope. The path you are trying to take will only cause more trouble. I say do the right thing and tell the truth
I am of one blood type my husband is another. 2 of my kids came out same blood type as me the third came out same as him. I don't know much about how blood type stuff works but it might be best if you just tell the truth. Good luck to you.