Thanks for the advice so far.
I have got a 55T motor in an SCX Crawler that I could use; it would be easier enough to drop out and put in. I like the idea of making a gate too; I have an old 2.4 stick transmitter that I could use for this too.
I could on the other hand program my Spektrum but to be honest I think kids prefer a stick transmitter, I know I did all those years ago but there was nothing else at the time.
My daugher has a mini Losi Baja Beetle, 1/16 scale I think but I was going to introduce her 1/10 Tamiya and start off with a cheap buggy, Fighter FX or something.