Hi Martillo:   Your MIL and FIL are lucky to have your help! The Seroquel and Remeron will likely take a few weeks to give benefit.
I think I will send a letter to both BIL's stating the clinical details; the financial details for placement (I have visited multiple assisted living facilities, memory care facilities, long term care facilities at FIL's request) and the details of what care is being provided now - sort of like Joe Friday - just the facts, ma'am!
It can be very time consuming and difficult to choose a care facility.  It is probably a good idea to share the info. and if others want to join in on making a decision, they won't be able to say they didn't have an opportunity.  My mom was between hospitals and skilled nursing facilities for the last 6 months of her life.  Even after visiting nursing facilities and checking ratings and inspection data (and staffing ratio) from a government website, that inspected and licensed skilled nursing facilities in our area, we still had problems with our choices.  All you can do is make the best choice you can, with the information at hand.
You can't go too wrong with just sharing the facts with a pleasant comment that you wanted to keep them informed. (and then let it go)   Their conscience will be their guide and let them decide what action they want to take.  They will each have their own would'a, could'a, should'a down the road, should they choose to ignore the information you share.  
Keep in touch and let us know how it goes.  Don't forget to take care of yourself!