His daily life fortunately abounds with number opportunities.
Matching buttons with buttonholes as he does up his coat, as he helps sort socks and shoes into pairs. as he counts, with you, the steps up to the library. As he sings ‘Five Little Monkeys’, for example, and counts along with his fingers.
Commenting, in a light and pleasant voice, ‘I wonder how many bricks high your tower is?’ when he is building is a gentle remark not an intrusion into his play. Keep ‘counting’ little and often making it a pleasurable activity for him. Take into account his current stage of understanding building on what he already knows. (Playing alongside your child, and choosing appropriate equipment to lay out at a setting, you avoid questions and tasks, which are too advanced for him.)