I go to St Lucia a lot with work, and went on holiday during lockdown. Having been going there for many years and knowing the place, it was not on my list of places to go on holiday. However, it was about the only place we could get to for a holiday (the combination of Covid testing and staff travel made for a very limited list of possible destinations) and we were very pleasantly surprised.
The island is, as many people have stated here, very much poorer than other Caribbean holiday islands, however many people there work in the holiday industry and are delighted tourists are back again, we found ourselves well looked after because of this. The airport is to the south of the island, and the main towns and most of the resorts to the far north. The drive is stunning and scenic, but can be a problem if you or your baby suffer car sickness at all. The northern towns are not attractive, and although there is a lot to do on the island much of it is nature-based, and probably not very baby-friendly.
if I were going on a Caribbean holiday with a baby (and having been on one with an 8 month old who struggled with the heat and humidity, we did not go anywhere jungly again for a few years, young children and babies in particular cannot thermoregulate in such climates as easily as adults can) I would be looking for somewhere that offered rest and relaxation in a stunning setting, rather than going for the local attractions. I cannot imagine that your baby will be much bothered about climbing a Piton, zipwiring across the forest canopy, hiking through the jungle to a waterfall, or visiting the volcanic crater you can bathe in. Nor will they be bothered about sunset boat trips, snorkelling or scuba diving. These are the things that make St Lucia different to other islands.
There are some truly spectacular resorts though if you have the budget. You will obviously be able to get away with just one room, so that will keep price lower than if you had older children. Top of my list would be Sugar Beach or Anse Chastenet. BBC Beyond the Lobby did an episode on Jade Mountain, which is owned by Anse Chastenet. The only thing with this resort is there is no air conditioning in most of the rooms as they are open to the sea air. If you want St Lucia but without driving to the north, Coconut bay is the only hotel on the south of the island. I used to stay there a lot, and it is pleasant but not much different to Barbados hotels. It has been refurbished recently. Of the hotels and resorts to the north of the island, I don’t know much. I stayed there for 2 nights in a budget all inclusive and could not wait to get out of the place. We’d stayed before then in a bungalow on a chocolate plantation up in the mountains, and drank rum cocktails whilst watching fireflies and listening to the bleepy frogs and thunder rolling in the distance. It had been awesome (but beach-less) and we regretted our decision to leave our mountain bungalow in search of a bit of beach.
I had a friend rave about the Body Holiday resort right up in the north, and there is a strip of resorts just to the north of Castries that are decent names but I haven’t stayed in any of them on this island (St James, East Winds, etc.) I would not go back to Rodney Bay or Gros Islets if you paid me (and that’s not as far from possible as you might think!)