Have just rediscovered the recipe for yoghurt cake, and since it needs no weighing of ingredients, DS1 could make it all by himself - hooray!
Recipe
1 pot yoghurt
3 pots of s/r flour
1 pot caster sugar
1 pot oil
3 eggs
Mix all ingredients together and put in muffin cases (about 10) and bake at 160c for 15 - 20 minutes
Easy peasy, you only need to help them with the oven bit.