We found the ship to be an ideal size 24 rooms each with a large window, 48 passengers and a total of 32 ish crew (including crew members and naturalists). The food was very good, the staff accommodating, the naturalists ranged from passionate to capable. Safety - of the passengers and the wildlife - seemed of the utmost concern to every member of the team.
Excursions were many and varied and we recommend you take as many as you are able.
Initially, we'd had some reservations about the level of activity that would be required of us. The spirit of adventure captured and transformed us into hiking, snorkeling, kayaking Grandma and Grandpa to no ill effect.
There was one daily event that was awkwardly timed: Regrettably, the educational talk given in the bar area at the top of the gently rocking ship came after a physically active morning and a full meal at lunch. Even those eager for the information often lapsed.
We did not take our grand-kids - unsure at what age a child might maximize his/her experience. In our limited observation (and acknowledging there are exceptions) the 10-18 range seemed optimal. Any younger and they might not have the focus or ability to enjoy some of the activities, any older and they seemed to be focused on more urbane interests.
Plenty of room for two people. Enjoyed the large window most of all.