There are very different rates at which new flyers learn. If someone has some aptitude for this, and is getting a friend to help them for a couple of flights then maybe a 4 channel more or less straight away is doable, but you can get yourself in a mess very quickly with 4 channels - and you can also have the most spectacular types of accidents as well.

Probably the biggest risk with 4 channels for new flyers is that they accidentally (or on purpose thinking they are ready for it) invert, or partially invert the plane. Three channel RETs just fall into a stall turn under these circumstances and almost recover themselves, whereas your aileron plane will need to be flown out of this orientation.

BTW - that was a great first flight.

Cheers,
Oz.