I think if I were you, I would book a regular room at Wilderness Lodge. Because your youngest is so young, you would only need 1 room. You would be close to Magic Kingdom (just a boat ride away). I would also look at one regular room at a moderate hotel, keeping in mind you won't have a balcony or anything to hang out on while the kids sleep. The value resorts have family suites, or you could get two connecting rooms at a value, if you want more space. You could technically all fit in one regular room at a value but it would be cramped. Play around on the WDW website to compare prices, WDW is definitely more affordable than what your TA probably quoted.