Most Helpful Guy
He may be aware you're pulling away from him, which is motivating him to try and lure you back to him with gifts and his unbridled attentiveness towards you. That's a noble effort on his part, but it's also a bit manipulative; especially since you told him you did not want him to buy you those things, and if he has half a brain, he's got to know you're going cold on him.
That doesn't make him a bad person, as what he's doing is pretty common. But you're starting to want distance, and he's doing everything he can to secure a life line in the hopes he'll continue to go with you.
I do not think you should let an event or something he gave you (which should have been unconditionally and not as an attempt to change your feelings about him) delay something you feel strongly about. Your relationship is no longer working for you and you're ready to move on. There's no easy way around this, and as long as you keep quiet, he still has false hope you might still be in love with him.
You owe it to him and to yourself to make a clean break, and you can't worry about feeling obligated, because all you're doing there is prolonging the inevitable. He can also use your silence against you by trying to make you feel even worse by saying how he did all these things for you while you said nothing about wanting to break up.
So, he'll be sad and hurt, but the relationship cannot go anywhere with just one participant, and the sooner you break things off with him, the better off you'll both be. If it makes you feel better, you can offer to return his gifts, and just say you're sorry he made plans to attend your banquet, but you felt he needed to know how you felt and you'd prefer he not be there.
There's no way around not hurting him, and the longer you draw this out, the harder it will be for the both of you. It's unfortunate someone has to be let down, but that's the way relationships go sometimes and it happens to all of us.