I agree with everyone who has said that if your alternative is a Value or Moderate, then a
DVC studio will be just fine!!
Obviously, there are larger and smaller studio rooms among the resorts but any of them will be nicer IMO than a Value and most will be nicer than a Moderate as well, especially given that you have an inside hallway and a balcony!
I wouldn't necessarily rule out BLT even though it's the smallest studio among the DVC properties. It's still larger than a value (300 sq ft vs 260 sq ft), but is slightly smaller than most Moderates which are 314 square ft except for CSR which is 340 sq ft.
Although you may lose a bit of space with BLT compared to a Mod, you gain a tremendous location for you and your kids. Hearing the ferry boats in the morning, watching the monorail and the buzz of being so close to MK. You can also take the monorail to Epcot. When returning to your room at night, you might catch the electical water pageant or see the MK fireworks. Being able to walk to MK is awesome and a huge timesaver! Plus, you generally have some type of covering when walking around the resort itself whereas the Values and Moderates are open to the elements when walking around the resort.
If space is your primarly concern, then OKW has the largest studios at 390 sq ft. I believe most of the others are around 360 sq ft give or take 10 sq ft. with the exception of Jambo House value studios which are about 316 sq ft.
Again, if comparing to a Value or Mod, you should love the DVC studios! They aren't quite as nice as some Deluxe rooms, but they are very nice rooms compared to a Value or Mod IMO.
Good luck deciding!