Wow -- I didn't know you could rent prescription masks.
Kim I wear glasses & contacts too. I don't like to swim with my contacts but I do snorkel. I'm blind as a bat w/o my glasses but the refraction of the water allows me to see more underwater than I can outside. Even without my glasses I can still see something. I do ask whoever I'm snorkeling with to stay near me just in case though.
Your DH will enjoy snorkeling even w/o perfect vision.