hi,
for good warm boots for young kids (water proof to below the ankle and good traction in the snow), I unfortunately could only come up with Timberland boots, could not find a cheaper option for my 2 year old last year! Again, while I did find some warm clothes for a 2 year old at Stanley, they were not proper ski attire as most brands don't make ski clothes for kids under 3. The place I found to have a good selection of 3 year old ski clothes was on TST side - the 2 sports wear/ski gear shops in the same building as Citysuper food court.
Depending on the ski resort you are going to, they may provide a good rental service - at Whistler you can rent EVERYTHING down to the ski mittens and helmets for a young kids. Have a wonderful trip!