Hi H44!
If I were you I would save yourself some frustration and buy a new Lionel LionChief ready to run set. They come with a remote control, power supply, O36 track and every thing you need to have his set up and running in minutes. More then likely you can run your old rolling stock with the new train, but they do recommend a 10 car limit on the 2-4-2 LionChief locomotive and consider each 1 of your old rolling stock as 2 cars if they don't have fast angel wheels. They have remote activated sounds and the steamers have smoke too.
The LionChief sets come with a DC power supply, but if you want to upgrade to a more powerful AC transformer you can and the remote control will work too. Also you could run it on a layout with Legacy if you go that far. The LionChief remote is specific to each model locomotive so you can run more then 1 train on the same track. If you have 2 of the same model they will both respond to the same remote. For example 2 silver bells locomotives will both respond to the same remote. One silver bells and one polar express will only respond to its remote. Lionel puts the name of the model on the remote.
$144.99 Lionel O 6-30207 Santa Fe Scout Alco RS 3 Freight Lion Chief Remote and Train Set
http://www.modeltrainstuff.com/Lionel-O-SF-Scout-Alco-RS-3-Freight-Train-Set-p/lio-6-30207.htm
$179.99 Lionel O 6-30233 Pennsylvania Flyer Lion Chief Remote Train Set
http://www.modeltrainstuff.com/Lionel-O-PRR-Flyer-Train-Set-p/lio-6-30233.htm
$189.99 Lionel O 6-30205 Silver Bells Express Christmas Lion Chief Remote Train Set
http://www.modeltrainstuff.com/Lionel-O-Silver-Bells-Express-Train-Set-p/lio-6-30205.htm
$219.99 Lionel O 6-30214 Peanuts Halloween Freight Train Set With Lionchief Remote Control
http://www.modeltrainstuff.com/Lionel-O-Peanuts-Halloween-Freight-Train-Set-p/lio-6-30214.htm
$279.99 Lionel O 6-30218 Polar Express Passenger Lion Chief Remote and RC RailSounds Train Set
http://www.modeltrainstuff.com/Lionel-O-Polar-Express-Passenger-Train-Set-p/lio-6-30218.htm
There are many more sets and more to come from Lionel
http://www.lionel.com/Products/Find...talogID=89&CollectionID=&searchWithin=Current
http://www.lionelstore.com/lionchief-remote-control-set
I wish they had the LionChief when I set up my grandsons layout. They love the remote control of the Polar Express and Silver Bells sets I had under our Christmas tree. They played with the Christmas trains more then they do with their layout. Now they want remote control for their layout!
If you decide to use what you have follow Stoker's advice and go to OGR's forum be sure to post some pictures of what you have and you will get your answers. I can't help you much with those other brands I am 99% Lionel in O gauge.
I am glad to see you introduce the boy to model railroading and your right to go with O gauge for the youngster they are much more rugged and dependable. My 4 and 5 year old grandsons can change cars and run the trains with little need for help from me. Keep an eye on him always because it is an electric toy.