Should we have bought a gift card as a thank you, and is my friend obliged to pay?

Just recently, my high school hosted a senior prom. It was a great time, but now I have two arguments with my boyfriend. He and I went together, along with a large group of our friends. After the prom we were invited to a friend’s home in the neighborhood. The night after, festivities continued at another friend’s house in Cape Cod. The parents of the two boys were very welcoming and open to offering their houses. After all this was over, my boyfriend suggested everyone chip in $10 to buy each set of parents a gift card to a nice restaurant and a generic thank you card signed by “The Group”. While this is a nice gesture, this is where I have two issues. First, I feel as though buying a gift card sends the message that we “rented” the place and are paying the parents off, especially since they expected nothing in return. I sent both parties personal thank-you cards. I think that the parents would have appreciated 16 personal thank you notes from each one of us over $80 and a note from “The Group.” If we wanted to do a group thank you I also feel like flowers or a fruit basket would have sufficed since we’re all poor teenagers. This leads me to my second issue. One friend of ours sent gifts to the parents before the prom, so she did not want to contribute the money to the gift card fund. I see no reason that she should have to pay, but since she attended my boyfriend thinks she has a moral obligation to contribute to his gift card fund. Who’s right?