two remote control cars on same frequency?

I purchased two Wild Fire (Fast Lane) remote control cars for my son-in-law and grandson. They operate on the same frequency (27.145Mhz). I opened it up to see if I could change the crystal set in one of them, but only the remote seems to have a crystal, the vehicle seems to have a coil setup mounted on a daughter board. Is there any way to either tune the coil or purchase a new daughter board (with associated crystal) to get the two vehicles to operate side by side without interference?

1000 thanks in advance for any guidance.

I don't think you can alter the frequency so easily.. you will have to buy another set with a different frequency…. or just ask them to play in different rooms lol