Hello, Maggie!
Congratulations on making your first family trip to Walt Disney World!
Of course you should aim for perfection, it's the Happiest Place on Earth, right? Go for it!
We've stayed at both Disney's Contemporary Resort as well as Disney's Polynesian Resort, and love each one for very different reasons. Staying on the monorail is the way to go with little ones at ages 5 and 2; weary little ones never have to leave their strollers if you wheel them out of the Magic Kingdom (or Epcot), onto a monorail, out at your resort stop, up an elevator right to their bedside. So very convenient!
Perhaps consider the amenities in each resort, and which you'll use most often. For example, if you plan to eat at Chef Mickey's at least once, will book
a Pirates and Pals Fireworks Voyage and want the
option of walking to Magic Kingdom Park, then consider booking your stay at Disney's Contemporary Resort. If, however, you know you'll never walk to MK, and intend to eat at least once at Ohana as well as Kona Cafe (Tonga Toast is a family favorite!), and will spend at least one day at your resort pool, then choose Disney's Polynesian Resort. While the pool at the Contemporary is great, our family really loved the Nanea Volcano Pool at the Polynesian. In addition to the 142-foot tubular waterslide, the children's wet-play area might be just the perfect spot for your kids to splash and play for a bit, and Mom and Dad will really enjoy the tropical feel while you're there as well.
If nothing but resort amenities is what will determine your choice, I suggest Disney's Polynesian Resort. For a first-time experience, you'll be spoiled beyond belief!
Best wishes for a first visit that's beyond your wildest dreams! Send me as many questions as you can as you make your additional plans! I'd love to help!