My wife and I just stayed in room 8140 (studio). We are Old key West owners and have stayed at Animal Kingdom, Vero Beach, Hilton Head as well.
The Bay Lake Towers Stueio was the tiniest we have ever been in and my wife and I could not even comfortably pass one another in the hallway leading to the kitchenette.
We were scoping it out to see if it would be large enough for our grandaughter, daughter & her husband and another infant soon to be born. The queen bed in the studio can not be moved because it is surrounded by a wooden frame affair that is attached to end tables. If the sleeper couch is pulled out I can't see where you would put a pack n play for your infant except out by the entry door where there is a small alcove for the door that adjoins the 1bedroom unit next door. We are owners at Old Key West and the square footage of the studio there is 390 sq ft vs 339 at BLT. That gives you another 51 sq ft which would make fitting in a pak n play for your infant a lot more comfortable.
We also thought we might select the BLT because of its closeness to the Magic Kingdom for my 2 year old grand daughter, however it is not as close as it seems timewise. It is a 10 - 12 minute walk to the Magic Kingdom that you won't want to do if it rains. There is no bus service between the Contemporary/BLT and the Magic Kingdom. You need to take the monorail to the Magic Kingdon so you must take an elevator to the 5th floor of the BLT and then walk across a walkway to the Contemporary then up and escalator to the monorail. This process will take you about 5-10 minutes
Then (suprise)the monorail travels in the opposite direction from the Magic Kingdom making a stop at the Transportation & Ticket CEnter, the Polynesian and the Grand Floridian before coming almost full circle and arriving at the Magic Kingdom. The monrorail trip will probably take you at least 15 minutes depending on how many people board along the way. So the total time from room to Magic Kingdom will be 15 - 20 minutes. The only time the trip between the Magic Kingdom and the resort is quick is on the return trip from the Magic Kingdom because you board the monorail and then the BLT & Contemporary are the first stop because of the direction the monorail travels in. After realizing that the BLT will not be as physically convenient as it appears we timed a few of the bus routes between the Magic Kingdom and Old Key West & Animal KIngdom and the travel times are usually about 20-25 minutes. Animal Kingdom Kidani Village studios are 366 Sq Ft and Old Key West is 390 Sq Ft. We may be sacrificing the view of the Magic Kingdom but if we get into the Anima Kingdom Kidani Lodge they will have more space and the Animals for the children to watch. I hope this information helps you make a decision.