As usual, it depends where you are trying to end up in DFW.
If you're going to downtown, RBD might be a better bet. The list below are all pretty accommodating of transient GA
Plano - ADS (sometimes busy with biz jet traffic) medium pricey for transients
North Dallas - ADS or TKI or T31
Mid cities - GKY GPM
North - AFW, 52F
East - HQZ
Ft Worth - FTW
N. Ft. Worth - T67
S. Ft. Worth - FWS
Basically get a sectional and see where you want to go.
LUV charges a landing fee of 5-ish bucks per 1000 lbs gross. Used to be free, but not too bad for an RV. As others said DAL will be $$ for fuel.