Congratulations!
I sailed on the Crystal Harmony to Alaska when I was about 5 months pregnant. I wanted to go somewhere cooler where I would be pampered a bit. The only time I had a problem with nausea was when we were going through the Inside Passage. It seemed like we were going pretty fast and there was a lot of motion. Being up on deck with fresh air helped.
Anyway, I pretty much did anything I would have done had I not been pregnant. I went sea kayaking, white water rafting, took a helicopter ride and settled on a glacier for a sip of champagne, had a massage (on my side), etc.
Your body knows your limitations and will let you know if you're overdoing it. STAY HYDRATED! Make sure you get enough rest, even if you have to take a few quick naps throughout the day. If you're travelling in May, the heat and humidity may take a lot out of you. Don't push yourself. Make your husband pamper you. Enjoy yourself!