You and Deb. We just spent the weekend with our five-year-old grandniece and her grandmother at our place. Aunt Debbie was in her element. Admittedly, half the activities she'd planned (and I'd helped print out—Unca Chack mostly serves in a support role, thank you) were ignored, and we spent most of her time awake today playing something she and Aunt Debbie thought of on the spur of the moment, but my wife had a WONDERFUL time.
But Deb knows that in 5-8 years (based on nieces and nephews who are now producing the new set of grands) she will become "good ol' Aunt Debbie" who is very loved but not actually needed. Christmas and birthdays will stop being events with wide-eyed unwrappings and turn into heartfelt (mostly) thank-yous for gift cards. (I will graduate from wierd Unca Chack to odd Uncle Jack—not nearly the same demotion, IMHO).
I will mention the babysitting thing to her.