I am hesitant to donate specimens at this stage in my life. Your second option is to set legally in your will how you wish to donate or dispose of your collection or certain portions of it to whomever you wish it to go. Talk with these people before you do this because, believe it or not, they may not want the collection. They simply may not wish to deal with it for whatever reason. In this situation, do not, I repeat, do not put any long term requirements on their receiving it if they agree to handle it.
Nobody wants a legal hassle.
At the present time, I have two agreements with fellow collectors, one simply verbal and the other written in a will. The verbal agreement, which the relatives are aware of, simply gives me all the individual's collection and materials dealing with minerals, fossils, collecting and geology books, lapidary equipment, and so forth. As I dispose of it in any manner I see fit, I have agreed to giving half the resultant money to the nearest surviving relative and the rest is mine to pay for my time and effort. This is a reasonable working agreement between friends. In the second instance, the will agreement designates that I am given the entire mineral collection of the individual to dispose of as I see fit.