Maybe you could order the online PDF and print a chapter that's eye-catching like "1975: The Appropriate Time for God to Act' or "1914 and This Generation" and leave it around to catch their eye. Maybe they'll read a chapter and ask for more.
I have no experience cold-dropping this book on somebody. I had a niece who left to marry a "worldly" guy and had been inactive, but my sister was constantly trying to get her back. She felt like her mom was right, but she just wasn't ready to go back yet. CoC cured her of that. Likewise I had an aunt who was fed up and her son (formerly JW) was now anti-JW. They hadn't gotten CoC yet. I suggested it and they both loved it.
Unlike your kids, they were all out already.