I've got a foot in both camps, mothering-wise; I've got two minor kids and four legal adults. Two of said adults have flown the nest and all four of them are firmly entrenched in the adult world - with jobs and everything!
Back in my Old Mother Hubbard phase, I used to worry a bit about how my relationship with the kids would change once they were “kids” no longer. If you wonder about the same thing, let me tell you a secret: it gets even better!
I've heard friends who are grandparents talk about how wonderful it is to be able to enjoy a child without having to be responsible for correcting it, and that's sort of how it is for me as the parent of grown-ups. Of course I worry about them from time to time, but they're finished; it doesn't matter to me once they've moved out whether they clean their rooms or eat breakfast. I can help them celebrate their successes and commiserate with their woes, but I can do it without following it up with, “Now go take a bath – USE SOAP and don't forget to clip your fingernails this time or I will clip them for you!”
Once you no longer have to be Nurse Ratched or The Warden from Cool Hand Luke, you're a lot freer to enjoy your children as people. Yours can evolve into more of a Lady Bountiful role, in whatever way it chooses to manifest itself when the mood strikes. If your daughter is having a terrible day at the office, drop off some zinnias and a chai at the front desk for her; take your supervisor son out for coffee and listen to his “personnel” stories. Send your soldier a care package of his favorite cookies and give the poor barista an unasked-for ride to his train when he has to open the coffee shop at 4:30 in the morning.
You don't want to become “that Mom,” the one who won't GO AWAY, of course, but since you are beginning to blossom again as a person in your own right you probably don't have to worry about that. Send them flowers, send them a funny card or a cartoon. Fill their car with gas. Ask them to dinner and prepare their favorite meal. It's a lot of fun to be able to add a little unexpected spice to someone's week, and it's great to be able to be the Mom without having to be the Mother.
Besides, as my own Mom used to tell us: It doesn't kill ya to be nice!