Take your kids to the Zoo sometime instead of Sunday School

It would be more effective in seeking to communicate the cost of following Christ to take them to see lions eating, than sitting in a classroom.

While rereading Let the Nations Be Glad, Piper references Richard Wurmbrand in reference to how to prepare for suffering in your call to follow Christ:

"I remember my last confirmation class before I left for Romania. I took a group of ten to fifteen boys and girls on a Sunday morning, not to a church, but to the zoo. Before the cage of lions I told them, "Your forefathers in faith were thrown before such wild beasts for their faith. Know that you also will have to suffer. You will not be thrown before lions, but you will have to do with men who would be much worse than lions. Decide here and now if you wish to pledge allegiance to Christ."  They had tears in their eyes when they said yes.

Wurmbrand goes on to say...

We have to make the preparation now, before we are imprisoned. In prison you lose everything. You are undressed and given a prisoner's suit. No more nice furniture, nice carpets, or nice curtains. You do have a wife any more and you do not have your children. You do not have your library and you never see a flower. Nothing of what makes life pleasant remains. Nobody resists who has not renounced the pleasures of life beforehand.."

This is a quote from 'Let the Nations be Glad' 

Practically, Christians in Spokane could take their kids to Cat Tales (Not exactly 'Wild Beasts', but there are not a lot of other alternatives in the Spokane area) for a spiritual lesson and tell them about Daniel and his trust of God, Foxe's Book of Martyr's, and Hebrews 11, Luke 9, and a whole lot of other Scriptures.

It might be the most relevant Sunday School Lesson of their life.

"Father, I ask and pray that you would help us count the cost of following you. The cost won't be felt in the comfy church seats/pews, in church programs, or in in a 'go to' church culture, but in front of lions, in front of adversaries of the cross, in front of having to deny ourselves and what we love, for the greater treasure, Christ Himself. May I lead my children in such as way that demonstrates in the steps of my life that I treasure King Jesus over comfort, family, the niceties of this life here in the U.S., more than living to an old age, more than paying off my home mortgage, more than ANYTHING or ANYONE. You are the pearl of greatest prize, the hidden treasure worth selling all to gain, the one who had freed my soul from the domain of darkness and Satan and given me the Kingdom. O that love would compel me and others to live resolved to bring you glory by denying myself, taking up the cross, and following You."