If thats the resort that you & FI picked & you both love it & would realllly like your wedding there, then I'd go with it!
Yes, you want to accomodate friends & family, buttttt, in the end, its your wedding!!! You have to do whats going to make you happy.
I don't want to sound inconsiderate, but its just my opinion.
Having a DW taught me that as much as I tried to keep everyone elses needs in mind, the only thing that should've been high on my priority list was me & hubby. And I'm only saying this because you will try to please everyone, but it won't work.
Sorry about the rant !
Really, I'm not into going to places twice either, but, everyone who went to our wedding had such a great time at the resort, that they ALL want to go back to Jamaica next year!
Why don't you just tell your sister that you really like the resort & were thinking of having your wedding there & ask if she'd mind going back! Maybe she won't mind!