Another benefit of doing good is that we get lots and lots of sawab (or what I call Happy Points when explaining it to little ones).Allah is so merciful that when we do good, he gives us lots of sawab, but when we do bad, he will only gives us one gunnah (Sad Point), as he states in the following ayah:”Whoever brings a good deed, he shall have ten like it, and whoever brings an evil deed, he shall be recompensed only with the like of it…” (6:160)
and here: ‘Who is it that would loan Allah a goodly loan so He will multiply it for him and he will have a noble reward?’ (57:11)
When trying to get the children to understand this concept, why not make it hands on? Take two jars (I made the Happy Point jar bigger to symbolise that we get more), label them, get some counters (different colours for good/bad) and voila! Either role play or when they actually do something good, get them to count out 10 counters into the Happy Point jar, and v.v. when they role play something bad, they only put one counter in the Sad Point jar.
Then the next time they do a good deed, you can remind them of this and how many happy points Allah is showering on them at that moment
P.S. This was initially used in Madressa to explain the concept of Sawab and Gunnah and the kids loved coming up and showing what would happen in terms of sawab and gunnah in certain situations!