The ferry to Anguilla is $20.00 each way pp
The departure tax is $5.00 from SXM to AXA pp
The departure tax from AXA to SXM is $8.00 for day trippers and $23.00 for overnighters.
Cauls Bottom is not near any beaches, it would be a 20 minute drive to the nearest best beach which is Shoal Bay East. Taxi's are expensive. Rental cars are $35-45 per day and the license is $15-25.00.
If it means anything, one of the reviewers for your B&B lives on the island, perhaps he had relatives staying there, I think you can do better pricewise and location. From your previous posts, it seems as if you are looking to stay over New Years, it is busy then, but with the pandemic, who knows.
Fountain Residences on Shoal Bay East are very nice, 5 minute walk to the beach. Very good pricing.
Good luck and happy planning.
Ellen