Wilderness Lodge is one of the most beautiful resorts on property. The pool area is fun and lovely, and the dining options are varied and good. Personally I think your kids would have a better time at WL.
I like the Contemporary as well, but overall, I think it's inferior to WL. Riding the monorail to-from is my favorite part of that hotel. (And snagging a room with a view of the fireworks, but you won't get that in the garden wing anyway.)
With a 1 1/2 year old and a 4 year old, are you considering returning to your hotel mid-day for nap time? (Having gone to WDW with a 2 year old and also with the same child as a 5 year old fairly recently, I would recommend it. WDW is SO overstimulating for kids. My daughter really needed some downtime. I'm sure it's double the struggle with two.) If so, I could understand why the monorail access would be valuable, especially if the route to Epcot is available at that time. (Honestly from Magic Kingdom, I would rather just walk than monorail.) You can take a stroller on the monorail without folding it up (leaving sleeping kiddos still snoozing). I believe the same is still true of the boat, so that would be a benefit on the MK days.