I wouldn't bring kids that age to the Contemporary. If your budget allows it, I think the most "magical" resorts for kids that age are the Polynesian, Wilderness Lodge, and Animal Kingdom Lodge in no particular order.
Sure the Contemporary might not be as kid friendly but it seems since your trip is short, the convenience of walking to and from the MK is the big draw. Seems worth it to me!
I agree with
@DisneyDreamer08 Aside from the fact that I'm of an age where the Contemporary Resort defines "Disney" to me, with kids that little and time on property that short, you're probably going to spend most of that time at MK. So the Contemporary will afford you the easiest and quickest way to get to MK and back. You've got Chef Mickey's right there, you're on the monorail so you can access the character meals and other amenities they offer easily, you've got boat access to Wilderness Lodge & Fort Wilderness...there are a lot of options from that one resort to get to and visit other resorts that are more "magical" if time permits. But with 3 days and young kids, it's all about MK. So Contemporary, if it's in your budget, is a great choice
I'll also add that of my last 4 trips, 3 of them were at Bay Lake Tower/Contemporary. My kids love it there and even though the last trip was not there, and my kids SOMEHOW managed to have a good time at Kidani Village and the Grand Floridian
my oldest (8 and change) confided to me that it's still her favorite place to be. To her, being able to walk to the MK, or better yet, monorail there and then do an entire loop on the monorail again before going "home" when the day is done, THAT is Disney magic to her. The shops on the 4th floor, the 4th floor deck and the connecting bridge where you can see MK, staying up to see the Electric Water Pageant, the cupcakes at the Contempo Cafe that are "the size of my head!" that is alllllll Disney magic as far as she's concerned. And with kids that are only 4 and 5, I suspect just being on an adventure and going to MK before going on a cruise is going to be magical as well.