I have a level 31 character that I do not want to level. If I wish to put points in the Vampire and Werewolf Perk Tree, would I be forced to level?

Nope, leveling Vampire and/or werewolf is totally independent of your normal level. Basically, you level those up by use the respective skills but that won't level up any of your regular skills.

If you want to level up just your Vamp perks and not the other you will have to play as the Vamp Lord most of the time.