Minisplit placement with Small Bedrooms

From reading Green Building Advisor, I understand even the smallest Daikin Quaternity (the brand I want) is oversized for even my largest bedroom, which is 185 sq ft, including the wall-length closet (with three 72-inch by 31 inch windows with low-E storms and plaster walls with no insulation, stucco exterior). Nine foot high ceilings.

Middle bedroom is 145 sq ft with two windows of that size;

Third upstairs room is 90 sq ft with one window, but is linked to a former sleeping porch that is 54 sq ft and full of south facing windows.

Although I live in climate 4a, and normal highs are 87 to 89 June 24-Aug. 18; normal lows around 70/71 same period; average dew point 67-68 in July & Aug, so far we have only used a window unit in that sleeping porch to serve smallest upstairs room, which is a home office & resorted to sleeping in a window-unit served room three to five nights a summer.

How bad an idea would it be to put a minisplit on the interior wall between the largest and middle bedroom, with a super short duct to serve the room on the other side? We are licensed foster parents, so at least some of the time, there would be kids on the other side of the wall, would the sound of us talking wake them up in that arrangement? Would putting the head in the kids' room be better in that regard?

If we did that, we could put the Midea inverter window a/c in the sleeping porch to serve the last room... still oversized, but at least it's more efficient than the GE window unit in there now?

Putting a minisplit in the upstairs hallway isn't really workable because it's a duplex, so the exterior wall is on the opposite side of the bedrooms from the hall; also, we don't intend to cool the downstairs, so there would be a lot of cooling loss as the cool air sunk down the stairs.

There is a closet between 2nd and 3rd bedroom that could hold a ductless unit to serve both, but that still leaves our bedroom, which again, would have a too-big unit.

I don't know if Quaternity has a ducted option. But even if it did, not sure how it would work, given we have no ducts (radiator heat); the attic is semi-conditioned but has a full plank floor (nine inches of space between plaster of downstairs ceiling and the floor).

What I mean by semiconditioned is there is no heating or cooling source up there, but closed cell foam and R23 rockwool has made it more comprable to the rest of the house. So if it's 80 degrees on the first floor, 82 degrees on 2nd floor, it might be 85 in attic?

(Going from memory)

Coolcalc says 2367 cooling load for all three bedrooms combined.

I want Quaternity because humidity removal is the most important for us. I don't like feeling too cold in a/c in the summer, and from what I've read from others' experience, dry mode in Mitsubishi often feels uncomfortably cold.

Thanks for your time! I know this was a LOT of data!

If you want a schema of layout, I can provide, if that is helpful.