Am I being a Petty Betty?

So, I'll try to make this as short as possible. I'm one of 8 grandchildren. We've always all been close, spent every holiday together and every Birthday growing up. Had family dinners regularly. Went on huge family vacations. I'm currently the only one of the cousins married with a child. One cousin is about to get married in September. He's really the only one of my 5 cousins and 2 siblings I'm not close with. He's been engaged for almost 2 years and he lives about 3 hours away. He didn't come to my wedding, didn't come to my housewarming, my son turned 6 months old today and he still had yet to acknowledge him or even meet him. His fiancé didn't come to my baby shower, she didn't even RSVP. We haven't even officially got invites and the wedding is 8 weeks away. No save the dates. Nothing. When they first found out I was pregnant at first they wanted my son in the wedding. My aunt (his mom) said to him one day a few months after my son was born that he should let Lucas(my son) off the hook for being in the wedding and he said 'whos lucas' he doesn't even know my kids name. So, his fiancé posts on Facebook (to her 700+ friends) that if anyone wants to reserve a room at a local hotel for the night of their wedding to message her for details. I want to text her not to even bother sending us an invite. Where I work my husband and I bid for vacation in October/November for the following year. Bidding is by seniority and only so much time off is allotted for each day. Well we didn't bid last year because they hadn't set the date or sent save the dates so the day of their wedding there is no time available to request off using vacation now. we would have to use sick time. Is it wrong of me not to want to use my sick time for this wedding? Is it bad that I don't want to spend money on an outfit (yes I would have to, I have nothing formal to fit my post pregnancy body). I don't want to be away from my kid for the night and waste it on someone who could give a fuck less about me. I don't want to spend money on a gift. The wedding is almost 2 hours away. I don't want to spend 4 hours in the car. I am for sure not spending money on a hotel. I just don't want to go. They don't acknowledge any milestones in my life, why should I go out of my way and give up time with my baby (who isn't invited, yet all the fiancées family is bringing kids). Am I being petty? Am I going to have to put my big girl panties on and go? Would you all go? I really don't want to go lol thoughts?

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