I've been following Pascale's coin purses
here,
here and
here. The last one brought back memories of a bag I bought in Warrandyte years ago.
The long cord/shoulder strap gets around my concern that the hand-held versions might be too fiddly to open and close when you're out and about (although I'd like to make one with elastic through the holes to see how that worked). I liked the bag so much that I made an upsized one that I used either as a bag over one shoulder, or as a back pack by adjusting the length of the cord and looping it under the buckle strap. I thought I'd share them with you.
Unfortunately, the leather version's a bit squashed from being under too many books in my bedside table, but what I'm trying to show is that the design has the same principles as Pascale's, but is a semicircle (or thereabouts) attached to a flat back panel which folds over to make the flap. Both versions are quite easy to construct and definitely worth a shot.
On another front, I made a 'standard' Pascale coin purse out of lined curtain fabric with a 4 year old on the weekend, and it was definitely an achievable project for someone of that age with a little assistance. I broke my hole punch trying to make holes in the fabric though, and found that cutting slits with scissors was a much better option!