Great Question
The adult members of the order of the arrow are advisors to the youth leadership, whether they like it or not. Along with donating a lifetime of cheerful service, they are more or less expected to impart their knowledge and wisdom upon younger generations. A perfect example is the elders of any indian nation.
I would Encourage each adult to relay his/ her imput on any subject, make suggestions and generally interact with the youth run meeting. Imput they add could prove to be invaluable. Other than that, I would encourage you to give them something to work on to pass the time.
An example in my chapter is Beads. Each adult makes beaded necklaces for ordeal, and brotherhood honorees, as a service to our chapter. After an ordeal or brotherhood ceremony, the adults bestow these beads on the newly honored member. It is our chapter's way of honoring them. (and it keeps the adults busy)
Any beading or craft that is benificial to the chapter, adults tend to be willing to do, including reskinning drums, making breastplates, etc. It helps cut down on the noise they make by chatting if they are working with their hands and listening intently to add their imput when appropriate.
Brandon
Former Serrano CC, 2nd Vice Cahuilla Lodge