Little ones are fairly easy
You can use stickers, magnetic systems, initials, smiley faces, etc. We would give rewards for attitude, promptness, etc. If they did them willingly or got them all done on time, sometimes (RANDOMLY) they would get a coupon for ice cream or something. Random works best. Remember that. That means, do not give a reward all the time. Every once in a while you can reward some aspect like quality or happy attitude and that will help improve the overall work.