Isn’t It Better to Do Good for Goodness’ Sake?

Questions about it being better to do good for goodness’ sake rather than to earn approval and avoid punishment and a good initial approach to take with someone who rejects God based on his “violent” and “oppressive” character in the Old Testament.  

• I want my children to do good for goodness’ sake. Doing it to earn my approval and avoid my punishment is the absolute worst outcome I can imagine, as is requiring them to relentlessly thank me for helping them find it—and I’m just a human!
• What's a good initial approach to take with someone who rejects God based on his “violent” and “oppressive” character in the Old Testament, regardless of good arguments about his being objectively moral?