Me personally i would tell.them just so no one can throw it back in your face later on that you didnt tell them, and besides you know it kills people to see someone they dont like being happy. I would tell them just to.get pleasure.out.of.knowing your happiness ruined their day. If you already know they dont like either of.yall then why would it even stress you out???
Why don't you two just get married and move away from all that? They are asking for you to turn your backs on them, do it and make a great new life.
I mean yu grown Wat would they do or even say to u its your choice to tell them or not if they don't like why would they care anyways