Although it wasn't our honeymoon, we had a fabulous time in Chile when my wife was ~6 months pregnant. The original plan had been Torres del Paine, but needless to say, the pregnancy scratched that. We just toured around the south near Puerto Montt and Chiloe. We saw penguins, drove to the end of the road, got tired of eating terrific seafood (hold the mayo, please), did a lot people watching, etc. Much less active than our pre-child standard, but still a lot of fun. She was tired much of the time so having a car and not being too far from a town was very useful.

Hawaii is pretty good too with a pregnant wife. We went to Maui when she was ~20 weeks and did everything we would have done otherwise except for hiking up to the top of the crater (beach, snorkeling, swimming in waterfall-fed pools, day hikes in the mountains, etc.). We did stay in nice digs (thanks FT) and eat nice meals, though, to keep the tiny baby happy.

If you have a low-risk pregnancy, and you doctor doesn't object, most destinations which aren't focused on wilderness hiking or scuba should be ok. I would suggest staying near whatever passes for a town, at least in the evenings, since having somewhere to relax is key. Frankly, you should get in as much adventure as you can handle now since pregnancy (low risk) is far less limiting than actually having a baby.

Have a great time and let us know what you decide.

Michael