Trevor said quite well most of what I would have said, but I'll add just a little to it. Being little doesn't necessarily have to involve "stuff" that you have to hide. When you where physically a child, what games did you like? What did you like to watch on TV? I'll give you some examples from my own life.
I personally have a total My Little Pony obsession that I indulge in when I have the time. The net is great for that. I do mandalas to relax, which in daily practice are just adult coloring pages. (To those who might have a problem with that statement, yes I know that there is a deeper meaning to them, but give me break on this one) I also love older kid and young adult fiction. You can hide a lot of material on a Kindle or Kindle app, and no one will know what you are reading unless they look over your shoulder or you tell them. I love the "five friends" genre, Babysitters Club, Saddle Club & Pine Hollow, Sweet Vally High, Beacon Street Girls, series like that. I was a total Sesame Street and Mr. Rogers kid, and still enjoy episodes when I can. Again, the net is a great resource for this one.
Yes, it helps some that my little side is a bit on the older end of the scale, but I bet you can find fun things that you want to do and can do. I did this completely off the top of my head. What can you pull from your own memories or what you find fun now?