My 2 y/o flew my 150 with me hands off for several minutes about two weeks ago. That was her first time up front. She's been in the back of the 172 many times (straight to sleep), but it was too nice not go up a couple weeks ago and the 150 hadn't been fired up for a while, so that's what we did.
I was pleasantly surprised at how much she liked it. She was banking left and right 20, 30 degrees and giggling with glee. She likes to aggressively pitch up and down, too, to get that "tickle in her tummy."
Very, very sad when I told her we had to land.
Again, 2 y/o.