The drive is really pretty easy just get on I-10 and set the cruise, itís almost 900 miles.
I grew up in El Paso so Iíve traveled the area, Iíve never been impressed with Van Horn and if it were me I would look at Fort Stockton and then Las Cruces.
Fort Stockton is a nice little cozy town. Good Sam lists a nice park there. In Cruces you have Mesilla Park and the legend of Billy the Kid and some of the best TexMex food in the world (itís worth a few days).
Like has been said youíll be driving through hundreds of miles of nothing so be mindful of it. Donít worry about the mountains, El Paso is at the end of them so you will go around them on 10.
Hopefully you have the time to enjoy the journey.