For your OWN health - as well as that of the Gliders - it would be good to find out what is causing the odor in the basement and remedy THAT first. If it is mold - it is dangerous for you even if you use something to mask the smell - the mold spores are still there.
AC/Heat vents are normally sealed with metalic tape to both prevent loosing heat and cool air into the attic or walls and to prevent the ducts from drawing in musty or dirty air from those areas. If there is a noticeable odor coming through the vents, they can be cleaned and sealed.
If the odor from your vents bothers you - you will DEFINITELY want to neuter any male gliders you bring into your home. Their odor can overpower an entire home. Most people will go nose-blind to the odor but any guests in your home will definitely smell your gliders.