Good deeds are Namaz, Quran, sadqa from pocket money, speak truth, listen to elders, no fighting, no anger, help your mama, clean own room, don't watch excessive TV or computer, share things with friends or brothers & sisters, etc. (If you want to improve any habit of your child then add to good deed list)
When a good deed is done then paste a flower on the tree.
For Girls: reward for good deeds could be pearls or stone collection, which can later on be used to make a necklace or armband, that can be worn on eid day
Good deed tree on chart or 3D