You bring up a very important question that is not easy to answer in one statement. Are you agnostics in the strictest sense "waiting to see proof you havent yet seen" or do you lean towards a belief in some sort of higher power but refuse to believe the negative religious dogmatic explanations you grew up with? Either way, your children will not be growing up in a vacuum regardless of whether they go to church with your mom or not. Even if they dont go to church, they will be exposed to religion via schoolmates, society, etc. and its better that you do not ignore the issue of their "spiritual" development because if you do, others wont and your kids will seek answers elsewhere and may become the very paranoid "religious fundamentalists" that you are not. Kids will want answers and you better be prepared to give them more than "I dont know". So what should you do? Help them make spiritually healthy choices.
This is what I would do if I were in your shoes and is what I personally consider spiritually healthy choices:
1) Tell them that there is no such thing as hell or the devil or a God that metes out eternal punishment and warn them that the religions and people that teach this are screwed up, backwards, misinformed, or however you want to put it that is age appropriate. This way they wont fall into the negative traps of fear or guilt or be victims of a cult or become "religious fundamentalists"
2) How about when kids ask "Is there a God?" Depends on how you answered my question in the first paragraph. If you believe in a higher power but not in religious explanations, tell them yes and that God is love and would never judge or condemn you and explore this part of your spirituality. I recommend reading "conversations with god" a non religious book on spirituality by Neale Donald Walsch and reading up on people who have had near death experiences (
www.near-death.com). Those who have had near death experiences vouch that there is no devil or hell and that God is love. These references describe a very healthy non-religious spirituality.
If you are not sure, say that you havent seen any proof of God, but if there is a God, he/she/it is definitely is not the way as described in point 1. I would then tell them to look in their heart and make their own choice on this and to let me know. If they choose to believe, I would guide them to the healthy directions I outlined in step 2 instead of sending them off to some religious fundamentalist churches.
Either way, Good luck!
GX