Not sure where to put this,

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I was going to adapt a real generic set of rules for my boys so they can play
40k. The reason for this is that my oldest son (who is 10) is painting legos and wants space marines for christmas. They live in
CA and i live in
KS, so i am going to try to do this at a distance. My ex makes things real hard to communicate with them much even via internet/skype.
I am going to get him some figures and paints to have fun painting/hobby side, but I also want to make up a "cheat" sheet of rules that they can use for fighting lets say a tactical squad against a tactical squad and be able to figure out things on the real generic side without using rule book and having me around as well as be able to explain something to them with them understanding it.
My idea was cheat sheet with generic sheet for youngsters to understand. My boys are smart but i dont think they might comprehend rules with out me there, so i need to make it streamlined and fun for them.
Is there any rules like that that peole have made already for their kids, or should i proceed to make some for my boys? Also any ideas?
Thanks in advance

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