Pushing buttons, TV Remote, playstation/wii controls. Avoid lightswitches and electrical appliances.
Get him to holepunch some thin card then thread coloured laces through his design.
Generally just helping Mum. All sorts of kitchen activities are good for fine motor skills. Let him help you make bread, the kneading and dividing the dough is good.
Can he use scissors to snip egg shaped balls of dough to make bread 'hedgehogs'
Loosely plait 3 strands of dough sausages he's rolled out to make a bread plait.
Making pastry, rolling it out, using cutters, putting shapes in a cake tin and filling them with jam/making mince pies, (seriously hot when first out of the oven so be extra vigilant if he wants to taste them while they are warm)
Do you have an old throw? Get him a large blunt upholstery needle with a big eye and show him how to do blanket stitch round the edge with a contrasting thick cotton as it's softer than wool.
Would he be interested in learning simple crochet, again cotton yarn is a lot softer on the hands than wool, but hasn't got any 'give'.