Just remembered something from the original post, 150 foot range... The car remotes are likely only about 30 feet. The cheap R/C car, probably about the same (less likely). Might look into wireless doorbells. Last one I bought only had one button, but there were 4 dip switches, up to 16 channels.
I'm only a hobbyist... but have found RF stuff tough to build from scratch, results disappointing and basically useless. Have been using ready built RF stuff, adding on to what I could find for a while. I've got better equipment, little better understanding, but still no urge to try building from scratch. It does take some skill, and probably the right test equipment. It's not too hard to make the circuit, just getting it tuned and tweaked. Kind of depends on your budget, time, and dedication. For me, I just want the gadget to work, cheap and quick (no sense of adventure).