Ruining my family's vacation... advice?

Every couple of years, my in-laws take their sons and their sons' wives/girlfriends on a special vacation. They have worked very hard for their money and this is one of the ways they are very generous with it. I used to feel really guilty about them spending the money on me to join them (I pay airfare, they usually rent a place with three bedrooms, pay for all food, etc). I came to understand that they really love doing this, though, and they look forward to it so much, so I try not to feel guilty, and enjoy it as well. 
On the last trip, my brother-in-law brought his fiancé (now wife). For various reasons, they are now not going on the next family vacation, which is already scheduled for this spring. My in-laws have already booked a place with three bedrooms, and still don't know that they aren't coming. The vacation is in the Bahamas. I have been feeling bad about this, knowing how disappointed my in-laws will be, and was not looking forward to the fall-out when they are told this at Thanksgiving. I just kept thinking, "At least my husband and I will be going with them." They do a lot of traveling alone, and I know the whole point of this is that they can spend time with their family. 
 They don't know I'm pregnant, yet - we are telling them at Christmas. I just looked at the CDC website and found out that the Bahamas were recently added to the list of places pregnant women shouldn't go because of ZIKA. I feel terrible, because I was so excited to tell them we'll be having their first grandchild, and now I'm afraid that the announcement will be tainted by the fact that their special family vacation will basically be ruined, because no one else will be coming with them. I've told my husband to go anyway, but (privately, between me and all of you), this does make me a little sad because that week is the last chance he and I will have to do someone special together before the baby is born - it will be our first - and I am also nervous because if your spouse is exposed to ZIKA or has even travelled to a place where it's been found, you're not supposed to have sex for the rest of the pregnancy. I'll be 27 weeks when he returns - I guess you can use condoms, but I don't think I'll want to risk it. 
This all sounds kind of babyish and privileged (I KNOW having these vacations is a very huge privilege - I grew up poor and feel VERY blessed to have such generous people in my life). I am not complaining at all, and I'm not even really disappointed as much as I am: 1) sad my hubby and I won't have this special time together or with his family before the baby comes, and even moreso, 2) I really don't want to upset my in-laws and disappoint them. 
Most of all, I'm afraid the announcement of our pregnancy will be "bad news" instead of joyous, because of their special family vacation being ruined. 
Advice on how to handle this? Should I still encourage hubby to go? How should I bring this up to my in-laws? Anything I can do to make this better for them? 
Thanks, and thank you for not judging. Like I said, I know this isn't a "real" problem relative to what so many other women are dealing with during their pregnancies.