Right. And people reading this comment will take it into consideration and end up doing the Blue Hole anyway, and then post about it on yet another Belize thread to say the exact same thing. And other people will read THAT comment and take it into consideration and end up doing the Blue Hole anyway. I love it.
So TRUUUUUUE! It's kind of hard to knock and experience, unless you have actually experienced the experience!
I live on Caye Caulker, Belize and have not done the Blue Hole.....YET! I've read all the posts and spoken to numerous others who advise against it.....because THEY HAVE DONE IT!
Let's face it, while the actual dive itself may pale in comparison to many, a majority (?), of other sites available in the meso-american coral reef zone, one cannot disagree that this unique geological phenomenon, appearing NO WHERE ELSE IN THE WORLD, is....well UNIQUE! Therefore, if for no other reason than to say "I've seen it firsthand, swum within it, dived to a depth of 130+' inside it and seen the "guts" of it!" one must take advantage of the opportunity to do all that, when it is presented to oneself! I plan on doing that at some point prior to moving away from here. Upon doing so, I will resist, with all my might, the urge to say to anyone whom might inquire about the experience "Yeah, I've done it, but it's not really all it's cracked up to be." BECAUSE, that's not why one does the dive....is it really???
On another note, more closely related to the OP's actual question and to the first reply. I've lived on Caye Caulker since 9/30/17 and have done 9 dives spread out over the elapsed time period (mostly in the San Pedro/Caye Caulker region), plus did 3 dives in April, 2017 (Turneffe Atoll), and can honestly state I've never experienced the conditions referred to by the first reply to the OP's question. This does not mean their observations are wrong, incorrect or jaded, it merely means I have not experienced them.
As such, and since the OP is seeking an enjoyable vacation on land and in water, I would wholeheartedly recommend Belize as a viable and worthwhile option. The mix between the incredibly diverse activities & sightseeing available on land, coupled with unBelizeable (sorry, I HAD to slip this in here!) varied diving options presented in the "Belize Coral Reef" region, would make for a potentially awesome trip for this couple. Hell, who knows, they might even have the opportunity to do a dive that's "not really worth it"....so say EVERYONE WHO HAS DONE IT, WHEN ADVISED BY OTHER'S WHO HAVE DONE IT THAT, "IT'S NOT REALLY WORTH IT"!!!
Regardless, to the OP, I would like to wish you all the best as you plan, logisticize and prepare for your vacation. I'm sure wherever you end up (I recommend Belize!), I'm sure you will both have a great and memorable experience...even if you might not recommend to others certain parts of it you might do, after being told yourself it's not worth it, by others who have done it!