Will a TMC work for my son?

The Atlas turntable will work on the carpet. You can use a single power source if you isolate it as a block, however TMCC makes things things easier. Are your sons engines TMCC though? Most of the intro sets are not

It's difficult to impossible to mix TMCC and conventional locomotives on the same track at the same time.  While some maintain it's possible, it's rarely satisfactory.  If you have separately powered loops, you can run conventional on one and TMCC on the other.

Thanks for replying so quickly.

This one will work on the floor Chris?

http://www.atlaso.com/oturntable.htm

I know his intro sets are TMC.  He has a GP-9, I found the instructions for it online and happily it is.  I thought I read a TMC II can run one non-TMC engine on the track at the same time.  I can't see how but maybe?  What would you recommend for a TMC controller and power supply?  The intro set came with a low end 80W transformer.

Conventional locomotives vary the power and also interrupt the power to change direction.  TMCC locomotives require constant power to the tracks, at least 12 volts.  Most conventional locomotives are cooking along at a pretty brisk pace with 12 volts on the rails.

People have run the two together if they get the conventional locomotive running in a single direction and then control the TMCC locomotive.  However, for other than continuous running with no stops, I don't see how anyone could be happy trying to run the two together.  The classic way to do it is to have a separate loop of track that is powered independently from the TMCC loop.

That 80 watt transformer isn't likely to run two trains very well in any case, so you need to address that.

You can find used TMCC CAB-1 and command base sets if you want to get in cheap.  If you're in it for the long haul, I'd go for the Legacy system, you'll have room for expansion, and it's a currently supported product.

You can run them both together but its tough, most important thing is the TMCC engine will be limited to the max voltage available to run the conventional engine, Where TMCC engines like 18V the conventional engines run about 9-12 V>

The CW80 will be straining with two engines but would work fine with either one alone

Yes that one will work, as long as you can get the track to it