It is not too late to hire a private lawyer. Private lawyers such as myself carry a much smaller case load so we have more time to devote to the client and their case. I handle cases like yours all the time.
It depends what County you are in. In Queens for example the DA wil not make an offer after indictment. In other places offers can get wrose or get better as the case moves along... it often has to do with the strength of the DA's case.
It doesnt matter what she thinks. She must tell the kids where the will is. If she doens't, under the Surrogates Court Procedures Act, the kids may summon and examine the Court can order her to give the information. If she refuses, she can be held in Contempt of Court and perhaps jailed.
You are not supposed to list an amount on the complaint. In any event, these are hard cases and often get dismissed on motion for failure to state a claim. Assuming you get to a trial the defense can make you look silly in front of the jury by pointing to how much money you asked for in the complaint.
The first question a lawyer will ask is what she fell on. Was there a liquid or something else on the escalator? There has to be a dangerous condition to have a case. You don't have a case if you fall because you are rushing. There is likely a Notice of Claim requirement that needs to be met within 90 days of the accident.