I agree with this exercise being perfect for concentration and attention.
The only thing that maybe, just maybe, I would have done diferently was to put these two activities on sifferent paper sheet. For small children is already hard to focus and well... seeing two exercises at once can interfere with their concentration and attention span. But this depends on kid's age I guess.
Matching items is always a good idea for small children and it can be made at home with any items like buttons, leaves, flowers, nuts and seeds, pebbles, fruits etc.
I always loved to create matching and sorting activities for Caleb.
Thank you for sharing your idea with us.
I think you're right, if it's for very young children, it's better to do it in parts, since they make that one, we'll see if they're still ready to make the other one right away and we should give them some free time.