How to go from here... future in laws disapprove of upcoming nuptials, should they still be invited?

There was always tension between me and my future in laws, in the eight years me and my fiance have been together, their dislike have been very obvious, and even once, when me and a mutual friend were visiting, had a very large argument over me (it was obviously a very hurtful and embarring situation to be in). We had been secretly planning the wedding for a month, and our friends and my family have already been told, and they are extremely happy about our announcement, and asking to help and pitch in (which I'm so grateful for). Since there is only 3 months left until the wedding, I am getting ready to send out the invitations, only my fiance hadn't told his parents yet, we already knew we were going to get a negative reaction, it wasn't a suprise when he told them (he went alone, to spare me from the hurtful things we know they would say or bring up). Obviously it went horribly, where they got into a screaming match, but overall they said they would attend. Now, we're on a tight budget, and I did not invite all of our friends or even allow some to bring a plus one to the wedding, that's how strict we're being with attendance. My problem is, it's great that his parents said they would attend (a year ago when my fiance moved out of his home and so did I to rent a place together, his mom swore up and down she would never come to our wedding if he moved out with me), it wasn't the answer I was expecting, but I'm having a real problem with the idea that they would be attending my wedding even though they disapprove of me, and don't wish us well, or given us their blessing. What I really wanted was a wedding with friends and family surrounded by warm wishes, a joyous occion... but I can't imagine them being there. I keep picturing us surrounded by smiling faces, and I look over, and could just see the sour look on their faces. The bulk of our budget is going to a great photographer, and I would hate for shots from my wedding of my in laws with disapproving faces, it seems such a waste of our hard earned money to end up having shots of them looking like that. What should I do in this kind of situation? I personally feel that if they aren't happy for us, they shouldn't come, why bother sending them an invitation? My fiance feels that they said they would come, who cares if they're not happy for us, the point is that they'll be there, because it's some kind of obligation (they are obligated to come because he's getting married), and to just ignore them on the wedding day. Should I just inform the photographer to not waste her shots on them? How do I create a buffer between them and us on our wedding day? Or should I save myself the heartache and just not invite them at all?