How to handle my future'in;laws?

My boyfriend and I have been together for over 3 years. We've definitely have talked about getting married and such. Before I got together with my boyfriend, he was having some financial issues due to his mother. She messed with his finances for a good year or so after we got together. After finding out what she did to him, I'm not a fan of hers. His parents have been nothing but nice to me, but for some reason, I dont like them. We live about 3hrs away from them and when they come and visit, my boyfriend always gets them something (ie: shoes, movies). I dont know why he feels obligated to do so or why feels bad and does. This past weekend when they came, get got them both a pair of shoes. As I was sitting there looking at them wearing them..it really made my blood boil. My boyfriend knows how I feel regarding the finances and knows that I would turn her in, in a heartbeat. I've made comments about not really liking them, but have never directly told him. How should I handle my feelings toward them?...especially if we decide to tie the knot!