make sure that their kids get exposure to more than just one form of "spiritual food," while keeping things peaceful.
I think you have answered your own question.
First, expose your child to other spiritual practices. Don't force it on them.
Second, let your child know he/she should use their rational thinking. Do not believe something simply because someone told them or a book says so. Always examine and investigate.
Third, teach by example. Be peaceable. Be understanding. Be mindful. Do not argue with your wife. When your wife says something truly listen with 100% of your attention with the goal of understanding her. Do not listen with the goal to either agree or to think up a retort to counter her point.
I have been studying Buddhism for 2 years and have taken up the practice of Soto Zen Buddhism. My youngest soon asked for a copy of the Tao Teh Ching. I was excited as Taoism influenced Mahayana Buddhism and gave us Zen Buddhism. I would simply asked him about what he read and would listen. About a year later he ask me to buy him a book on Zen Buddhism.
So, great question. I guess one great question for any person to ask themselves is "What is the purpose of spiritual practice?" Is it not to experience life to the fullest? Why are we here? Is it not to learn that we are not separate from one another? Religions that divide will become self evident.