Is there an adapter available to be able to use lenses for old AE-1 Program camera on my husband's new T2i camera?  If yes, what are the pros and cons?

Basically I wouldn't bother. Yes, such adapters do exist (see the above referenced article), but they aren't very good and they are inconvenient to use.

Unless you have a very special (expensive) FD mount lens (like an FD 85/1.2 or 500/4.5) the results you'll get simply won't justify the effort and inconvenience and loss of speed and quality of using an adapter.