Hi PamG, and welcome to cruise-chat.
We cruised with our son twice when he was a toddler. True, it's more work than traveling without a child, but it's actually less work than being home with her for a week. No cooking, not as much cleaning, for instance. I don't know if this is your first cruise, but if it isn't, you will notice a difference. Just go with the attitude that this is a family vacation rather than a romantic getaway, and you'll be fine. In reading your posts, I see you're there already.
We once went on one of the glass-bottomed tour boats with our son when he was little, and he was fine. It was a large boat--big enough to walk around, and had a roof for sun protection. But, as Penny cautioned, make sure she doesn't stand on the benches. You can inquire about that when you get onboard the cruise ship. We also purchased a coast-guard approved lifevest/swimvest for our son, which helped put our mind at ease during water-based excursions.
As far as eating, what does she enjoy at home?