DON't Accept anything yet,
I agree with that, given the new information about an offer to a school that DID accept the applicant. That changes everything. When my DD got a 3 Yr. AD to a Private, and a 4 Yr. to our in-state Flagship, I asked the ROO at the 3 Yr. AD school if she could accept the 4 Yr. AND the 3 yr. AD, and attempt to upgrade the 3 Yr. AD to 4 Yr. The answer was that you must decide on one to accept. I was also told it would be highly unlikely to accept the 4 Yr. to the Flagship, and then have Cadet Command approve a transfer of that 4 Yr. award to the 3 Yr. AD school.
In your shoes, I am not sure what I would do. First, I would attempt to get in, through Appeal, to the 4Yr. option school. Get the Cadre there to help if possible. Problem is you only have about three more weeks to get that done. If you get into the 4Yr. award school, you're done (maybe... see last paragraph). If you don't, I would see ask the 3 Yr. AD cadre if you have their support, then to ask Cadet Command to upgrade the 3 Yr. AD award to a 4 Yr award.
Last thing -- since you didn't get into the 4 Yr. option school, the Admissions committee thinks most of the students there are/were more prepared academically that you are. Given that, what is the chance you will excel academically at a place where you are less prepared than the students currently attending? What good is it to get into a school where you will struggle to get Bs? (there are possible benefits, but only you would know how you would respond is that circumstance... work even harder, and rise up, or be discourage and founder). This assumes of course that Admissions knows what they're doing when they try to match an applicant's preparation with their own standards and workload. Keep in mind that your GPA 3.5 years from now will play a very important role in defining your position on the Order of Merit List, and thus your Branching options. If you think you will likely be a B student at the 4 Yr. option school, and an A student at the 3 Yr. AD school, that is a very important factor you need to consider.