Ask or don't ask???

My husband and I are going to be looking into seeing what we qualify for in a mortgage hopefully soon. I was thinking maybe if we don't have good enough credit that I might ask my grandpa to be a cosigner. He has great credit and helps me a lot. He helps me pay for gas when I need it and pays for me to go to the dentist and eye doctor when I need to. I've asked to help with vet bills, but usually find a way to pay for it myself in the end. My husband said he most likely could work a budget out to handle about a $500 a month payment (we can do that where we live, the house just won't be fancy or really nice and that's ok) so my grandpa most likely would never have to pay because we are really good at making thing's work. Would it be ok to ask my grandpa if he would do this with/for us?