I'm not familiar with the SVI, but given the comments above and what I've seen in the past regarding the SVI, I would probably stick to the BVI/USVI. And we've got a 3.5 year old who we've taken sailing since he was 6 months. Even moved our boat with him from St Lucia to the BVI when he was a bit over a 1.5 years old.

My main reasons - it sounds like this is her first sailing trip? Given that, you really don't know what to expect from her. She could be miserable. In the BVI, you'd have many options if she was miserable. In the SVI, fewer options. With a 1 year old, I'd rather have more options. When we did our St Lucia to BVI trip, it was my sons 4th week long plus trip so we knew what to expect. Even so, I knew if he was unhappy with the longer sailing time, that worst case we could stop along the way and I could have him fly out with my wife. Fortunately he loved it though.

We always made sure to bring what we needed. Diapers, baby wipes..etc. We also brought a small pack and play (smallest they make I think). We also tried to have A/C most of the time. Whether we ended up on a boat with genset and A/C or used shore power. My son gets hot easily like I do so it was good to have a cool place for him to nap and sleep. And finally, we brought our own life vest - wanted one we knew fit well and would keep him afloat if needed.