Here are what I would consider in picking one over the other:
With 3 children, I think that you will find yourself spending quite a bit more time in the room than most people, so the room and size will matter more. If the kids still nap or need to sleep earlier, it will be quieter at OKW for them to do so because of the space of the unit. If at BWV, just send the non-essential adults off to enjoy the BW while the kiddies sleep!
OKW: Much larger 2 bedroom, esp. in the kitchen, LR and balcony areas
BWV: Will be smaller, esp. in the common areas
OKW: 3 real beds, 1 sleeper sofa, an extra loveseat sofa, as well as a comfortable armchair plus ottoman that my kids fight over to sleep on.
BWV: 2 real beds and 2 sleeper sofas
OKW: Washer and dryer are in a separate room near the front door which helps muffle the noise.
BWV: W/D are in a closet in the LR right in front of the master bedroom door. The accordian doors do NOTHING to muffle the sounds so don't plan on doing any laundry at night esp. if anyone is sleeping in the LR or anytime the kiddies are napping. I would go the machine first thing in the morning as an alarm clock to the rest of your party and hopefully place in dryer before heading out or first thing when you get back to the room. Warning: The w/d is LOUD!!!!
OKW: Larger dining table for sitdown meals and "converstions" around the table. Also large table on balcony.
BWV: Much smaller table with a bkfast bar that is o'kay for the kids, but we just used for storage. Little coffee table on balcony.
OKW: Nice walks around the complex - grass, trees, water views
BWV: Nice walks around the complex - great people watching on the BW
Since 1 to 3 of the children will probably be in strollers, so keep the park access in mind. I personally prefer BWV when pushing a stroller. I don't have to struggle with folding a stroller to at least 2 of the parks. 3 parks, if I take the monorail from MK to Epcot and then walk through the park. It is nice when the kids are sleeping to push them straight to the room without waking then up when getting on and off the buses.
OKW: Buses or car to ALL four parks
BWV: Walk or boat to 2 parks w/o having to fold up strollers.
OKW: Plan to eat in more or have to travel more to eat out.
BWV: No room to eat in, plan to eat out more. More choices within walking distance.
OKW: If you will have a car, more convenient parking. Will be able to go off site for groceries and meals.
BWV: No car is preferable or plan to park it for the duration. Having a car can still be nice, but not as convenient as at OKW - valet or plan to walk further to park.
Have fun making your decision!!! I'm sure that you will have a great time where ever you wind up staying.