I don't think you're wrong at all! We had an Intimate/Escape wedding and didn't have an at home reception (we initially planned to have one but my mom passed away unexpectedly 4 months before the wedding). My best friends still threw me a shower and we had about 20 guests there. They all knew they weren't invited to the wedding (we had 8 guests at our wedding) and they knew there wasn't any other kind of reception, but they still came to my shower. DH and I registered even though we both had our own apartments and didn't need anything, but it was nice to "upgrade" a toaster, crockpot, bath accessories, sheets, etc. We got a ton of presents which we were really not expecting! Then, my former roommate threw me a fantastic bachelorette party and again everyone invited knew they were not invited to the wedding. And about a week before the wedding my job threw me a surprise shower, which really was a surprise because I'd only been working there a couple of months.
So, in my personal experience, it doesn't matter that you're having a destination wedding and not inviting all these people to your wedding. I am a stickler for etiquette in most things but I think with destination weddings the rules have changed. You should get a shower - like you said you only get married once! Your MOH or BFF can throw it and invite your friends, close family, DF's close family. Or how about a co-ed engagement party? There are a lot of options - have fun!
ETA - most friends and close family members are going to want to celebrate you and your marriage anyway, even if they aren't coming to the wedding, a shower is the perfect way to celebrate with them!