I haven't seen any other mushroom hints, other than when I discovered that if you are really quick, and there are kids nearby a spotted mushroom, you can get 2-4 kids on a mushroom without going into pause mode.

I'm usually more interested in mushroom in games that aren't finished (i.e. haven't gotten fishing and/or GC) since the effort to collect the mushrooms is more valuable to the villagers. Though just this morning, when a red mushroom popped I put 7 kids on it! I'll usualy just ignore it or find a nearby kid.

It seems to me that mushrooms seem to appear more often if they've been collected more recently, but I haven't found anything to base that on, and the mushrooms don't appear in the log.

I think I have spotted the places where they are most likely to appear, so if I'm "mushroom hunting" I'll scan around the edges of the board.

Though sometimes it is really frustrating to spot a mushroom and then have to go get the kid (I'll use the "M"=map option if I need help) and then by the time I drag the kid over to the mushroom it disappears.

Or the kid gets the mushroom and then gest stuck behind the rock on the east side or the food bin itself and loses the mushroom before it gets to the bin.