Yes, The farm is very close to Orient Beach so you can stop there and incorporate it into your visit to this famous beach.
Yes, I know you will be starting from Philipsburg, that is why I saved it for the end of your day. There is also a Zoo in Philipsburg which may be of interest to you or your group.
There are a couple of small museums on the island, I'm not even sure if they are open, it's been many years since we visited them. One is in Philipsburg and one is in Marigot, in the Marina Port La Royale.
Hope this helps.