Fort Davis isn't very big, but it makes for a great get-away. For historians, the Fort itself is the attraction. It had to have been a rugged assignment in the days of its operation. It is remote by today's standards, but must have been the end of the earth for the soldies of the 1800's.
The For Davis State Park is delightful. I highly recommend a stay at Indian Lodge. It was built in the 1930's by the work program, and the facility retains all of the charm of the era but the comforts of today...air conditioning and private baths. Expect amazing views, great hiking and a short drive to the McDonald Observatory. But I suggest finding a weekend before or after the summer heat.