Bit of a tough question as it depends on how adventurous both you and your husband are and what (if any) lines there are.

A general first recommendation I'd make to any (hetero) couple looking to add a toy to the mix would be the Neo. Its relatively inexpensive, has a definite "naughty" factor for couples that have never used anything like it before, and performs well without being too intimidating. Should enhance his orgasm and if used in the right way the little vibe will make things nice for you.

Does he have an open mind? My wife and I just recently started exploring male anal/prostate play and so far the results have blown my mind. Takes a while to get past the hang up that a lot straight guys have that its somehow gay to like anal, but if you can work past that the results are pretty impressive. The Aneros Helix was the first anal toy for me that we ever used. Have to read the instructions (very un-male I know) and might be best used in a mutual masturbation type setting, but its a pretty good taste of the fun he can have if he's open minded to opening his back door.

Good luck to you both and enjoy!