Well then it simplifies things a bit.
The following TGs on TxWARN Moto system will probably cover what you want.
Using the Clodine Site (004) program the following TGs:
Katy PD1, 2, & 3 (9456, 9520, 23536); Harris Co. SO Dist 4 Disp and Tac South West (9008, 19152); Harris Co. Constables Pct 5 Disp 1, 2, & 3 (11504, 16720, 10000); as you will be on the border you might want to add Ft Bend Co SO Patrol 1 (2256) to the mix. DPS does not use the analog system anymore so its either add the P25 system I mentioned earlier or monitor them on conventional (it is simulcast), what you will want is the 155.4675 Houston Dispatch (it is repeated), 118 NAC and/or the P25 system's TG 2273. That will keep you apprised of what is happening LE wise for the where you will be.
Fire I am less clear on, certainly the Katy FD 151.1150 (127.3 PL); maybe West I-10 FD Disp 460.2500 114 DPL, Tac1 461.8250 115 DPL, Tac2 453.1625 116 DPL (note these are called COMM 20, 21, 22 by the Cypress Crk Disp Center, the 911 center that dispatches them). Maybe someone else can comment about the FD coverage in the Franz Rd area near Grand Pky, I am not too sure about there. In addition your family probably can tell you what FD covers their area, I know Katy FD covers where you intend to stay.
If you have an interest, you can always add the Life Flight Disp TG (from the analog sys) to your line-up. The west base is just east of where you will be staying on the N side of I-10 at Memorial Herman, Katy.
Hey Lou, I recently moved to Katy (I-10 & Mason Rd) and I am looking to program my 396xt.. You don't happen to have a freescan file with the above frequencies do you? The whole txwarn system looks so confusing to me..