Close “friend” egging me on about ex.

I broke up with my ex about a month ago. Even though I did the breaking up, it was on good terms and hurts still. I respectfully told her we should remove one another from social medias, etc. Fine, that really helped me move on, but my school close friend has her in his friend circle too. He wouldn’t stop talking about her, even directly after our breakup, like to the point of rubbing it in and I got a little mad at him. He also kept bringing up that he’s going with her and others to a game, they go and he posts photos with them having so much fun, of course he told me 2 weeks ago “we would have invited you but you know”. Basically all over his snapchat he posted videos and photos of how much fun they had. He even texted me earlier that day about her, and he tells me “you need to move on”, dude you won’t stop talking about her. Is it petty that I am tempted to cancel our upcoming trip because of this? My actual childhood best friend wants to drive with me instead. The people who’d be going on this original trip include this friend, another who said he’s cool but was in the photos with his arm all around her, and someone idc about. I think hanging with them now would make me sad or upset. Especially when the day trip is 2 hours one way. I’d rather spend the day driving 2 hours to Lake Geneva with my best friend.