My grandsons are visiting and the youngest (16 months) and oldest (2.5 years) both love it. As soon as they see me, "Pawpaw, train?" and lead me to the train room. We started out with a Lionel LC Polar Express set. Plug in wall-wart power directly to the track. We've grown to a 12'x8' L shaped layout with 4 LCS switches and added a LC+ switcher. Recently added VL Reefers and Legacy 990 base. About to add VL stock cars and the WiFi module.
We've been running the Polar Express and the switcher simultaneously with no problems. We are controlling the switches and reefer freight sounds with the Cab 2 remote, and operating the locomotives with their respective remotes. A grandson on each knee and a remote in each hand and a 90* crossing... you have to be on your toes at all times.
We also have several lighted structures running off track power and all of the PE cars are lighted, too. There's a spotlight car, too.
When will I hit the limit on the wall wart power supply, and how will I know?