After a little bit of research online, I think I've found one of the loveliest ideas for getting kids into coding: A storybook written by the smiliest woman I've ever seen, all funded on Kickstarter:
The book goes beyond introducing kids to Ruby, it also touches on topics like development principles and open source philosophy.
If your child is old enough, then little projects to get them into coding would also be a good idea.
Try and make the projects relevant to what they're interested in.
For example, if your child is really into Pokemon, you could work together to build some personalize Pokedex software to categorize and detail all the different Pokemons.
Finally, as someone recently told me, there are plenty of things your child should be enjoying at this point in their life. No need to get too hard on their case about "working hard" just yet, it could even prove detrimental if they don't genuinely enjoy it!