It never hurts to ask (it may hurt a little if they say no) but if done in the right way it would be okay-I'm sure your T would be honored to be invited and it's really up to how they view boundaries-I've heard of T's going to the ceremony just not the reception.
I've totally thought if I get married-I will definitely be inviting my T-and I'm almost positive he would come to the ceremony!
Congrats!!