should i cancel on him?

So what you weren't his very first choice, that is part of life. Don't cancel just because he was blind at first, it doesn't mean that you can't become his number one. Go with him it could be your chance to make him fall for you.

Of course you shouldn't cancel. You already said yes. Would be very rude to cancel.

So he asked others. Big deal. Think of the "last but not least" thing.