Here's one idea for you. Years ago, a previous owner of my house cut down a large silver maple, which left a stump approximately 30cm high and 65cm across. His solution for hiding the stump was to dump a load of cobbles on top of it. (he also had a pond dug next to the stump and hid the pump between two of the root flares under the rock). The cobbles are of mixed shapes and average about 15-25cm in diameter/max length. Here's a photo:
I added soil between some of the cobbles and planted several ground covers: Snow-in-summer(Cerastium tomentosum), a sedum identified as Sedum crassula (although I doubt that ID), and a creeping phlox (Phlox subulata). This gives me a bloom season of April - early July, after which it looks a bit ratty for a month until the Cerastium comes back. I could add a New York Aster if I wanted to have color later in the summer, but that's a bit too tall for my taste.
Now, I doubt that these plants will all work in your climate, but I'm sure that you can find succulents native to your area - or to a similar South African climate - that will work for you. The advantages of using rock here are that it's a permanent solution (and will prevent your children from eating mushrooms), it's pretty inexpensive, and with the proper choice of plants, it's maintenance-free.
