If you make a stop over in Mission Tx in one of the RV parks and cross at the new bridge of Anzalduas, from the bridge to the highway is an easy strech and you avoid going through Reynosa.
From the bridge to highway 40D toll road it is an easy strech on highway 2 to the 40 and then it splits into 40(libre) and 40D(cuota), the D stands for toll roads.
You will have plenty of time to reach the camp ground and avoid travelling at night, Houston to Monterrey is aprox 505 miles, Mission to Monterrey is about 150 Miles, Houston to Mission is about 360 miles.
navegator