I agree with other buyers that you shouldn't do anything more if you already got the house on the market. If a family really finds the lack of full bath a problem, they will bid accordingly.
I had the same situation with my 2BR condo. I only had 1 small bathroom because my home is an older brownstone. Lotsa couples who didn't bother to read the listing carefully came to see it anyway and ruled it out because of that reason. After one price drop, I got an offer from an older lady who appreciated the home and didn't mind the lack of 2nd bathroom.
Also, honestly, I am now looking for a home and don't even think twice about bidding on a home that had 4 BR and 1.5 BA. As long as there is potential place for a 2nd BA and the price is right, it's not a huge deal.
Also, may I add that the pictures don't do justice to your home, they seem rather blurry and aren't taken at the best angles. More would be nice too! Max. of 9 is allowed on realtor.com so I would ask your agent to retake them and post 3 more 'cus it's all part of marketing and getting people to see your home! Also, make sure the best photo is shown in list view. Entice them to click for more details.
Good luck!