I bought Marcus a book about a ladybird who falls out of her tree, and has to use the Tree Directory in her apron pocket to find her way home. Each page has a map and a little story, she meets characters who give her hints, and after each page you have to look up a branch, twig or stem in the directory at the back, eg Fruity Way - Map 5 E4, or Termite Tunnel - Map 2 G1, or Blossom Drive - Map 11 A3. Marcus loved it, but had a bit of trouble understanding the grid reference part. The maps were fairly simple and not too big, and he could usually find the street without needing to grasp the reference bit.
Since he is interested in maps, I thought I’d push it a little further, and I got out the Melbourne UBD and showed him how to find my old street in Elwood, May Street. On a UBD page there is about a thousand streets, so he understood the need to use the reference to concentrate on a square.
Anyway - I ended up looking up streets with funny names for him to find, and I have decided to call this new game Moon Street, Moolap, which was one of the first ones.
Here is a sample (you may want to look these up to verify).
Marcus St 7 A1
Michael St 11 K10
Catjump St 48 G1
Dog Lane 66 D9
Moon St 68 A9
Lion St 45 A9 ... that's about where we ran out of puff.