That is a hard one. I would first talk to your wife and ask what she thinks and go from there. My personality would be more of a parental unit, offering advice and such. But would also depend on the kids.
I think that it really depends on the attitude of the children and what they think of you. They are in their 20s and they should not demand nor require a lot of attention. Just make sure you presence is visible and make sure that they know you are not 'intruding'.
