One thing to consider: I'm not sure about Texas, but lots of states limit the farm exemption to a radius of 150 miles of your home (Farm). I don't know where you camp, but if you travel more than a couple of hours to get there, the farm tag may not be the best option.
Here's what I found on the Texas DPS site:
Texas DPS
FARM TRUCK
The registration fee for a commercial motor vehicle as a farm vehicle is 50 percent of the applicable fee under Section 502.162.
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The vehicle may be used for:
Transporting the person’s own poultry, dairy, livestock, livestock products, timber in its natural state, or farm products to market or another place for sale or processing.
Transporting laborers from their place of residence to the owner’s farm or ranch.
Transporting without charge, materials, tools, equipment, or supplies from the place of purchase or storage to the owner’s farm or ranch exclusively for the owner’s use or for use on the farm or ranch.
Transporting the owner’s family:
to attend church or school:
to visit a doctor for medical treatment or supplies: or
for other necessities of the home or family.
May not use a vehicle registered under this section in connection with gainful employment other than farming or ranching.
May not use a vehicle with a "FARM TRUCK" license plate to tow a trailer with a "TOKEN TRAILER" license plate.
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I guess you could say pulling your trailer is a necessity for your family.