I have an air mattress in my owner's locker that would allow us to do a 1BR for a configuration like this.
However, you are about to have a teenager, so whatever plan you make might just fail in a couple years.
With this kind of age spread and uncertainty, an option is to just rent points for what you need for this particular trip, depending on who is coming. The Kidani 1BR isn't hard to get, even at 7 months, and should work for a while. The VGF 1BR is also luxuriously huge, and someone can sleep on an air mattress next to the tub. Both are high priced in the system, so they aren't terribly hard to get.
Allow me to present another idea. Poly. If your oldest is responsible, you don't plan to do much cooking, and you don't mind the laundry room downstairs, two poly studios might be just the trick for now and also longer term. Or one poly studio if you're a person or two short. Poly also isn't too hard to book and can be done with rental points at 7 months. My five year old happily slept on a crib mattress in the extra Poly bathroom. The renovated rooms have a double Murphy sofa bed that's NICE, plus the single Murphy. So they comfortably sleep 5, maybe the fifth needs to be a child for the single bed.