The key is to start out slow. When your children are too young to read, but old enough to understand stories, read every night to them a story from the Eddas and the Sagas. To avoid scaring the children, and giving them nightmares, I would suggest that you leave off the scarier bits. For instance, when you read them the story of how Thor dresses up as Freyja to regain his hammer, once the hammer is place upon his lap simply say, " and that is how Thor got back his hammer". A 4 or 5 year old child does not need to hear how Thor then uses his hammer to split the heads of all the Jotuns open killing them ! When the children are still in the playpen you could surround the crib with pictures of our Gods and Goddesses, and even give them a doll that represents one of the Gods or Goddesses. This will place the Gods and Goddesses directly into the hearts and memories of the children. I think just about everyone as a child had a favorite doll that they loved.
When they become a little older buy them a set of Eddas and Sagas to read . But do not force them to read them ! The quickest way to turn a child against something is to force them to do it. Cartoons are another way to build an interest in our religion. Thor and the Avengers cartoons I believe are available on DVD, and will introduce them to our Gods . As parents you just have to make sure that you make the distinction between our real Gods, and the cartoon characters. There of course are movies out there as well about the Vikings, and Thor which could also have the same interest building effect on children.
When the children are too young to participate, but old enough to understand what is going on, allow them to watch a ritual that you perform, and become familiar with the structure of the ritual. If they ask questions, even during the ritual, do not tell them to be quiet, answer their question to the best of your ability, and then continue. I am a firm believer that the Gods understand exactly what we are doing during rituals, and will not be offended by a child interrupting to ask a question. Remember our Gods have children too, so they more than likely have had similar experiences, and will in my opinion be sympathetic.
As the child grows in knowledge, slowly give them small tasks to do during the rituals. Let them pour the mead, ( or whatever drink you use ), and explain that this is something the Valkyries do in the halls of Valhalla. As they become more and more comfortable with the ritual process, allow them to have a bigger and more important role in them . Eventually you can let them perform the ritual, as the lead, with the parents as the helpers. Showing them that you trust them enough to lead an entire ritual by themselves will give them confidence in what they are doing, and pride in their accomplishments.
The final thing that I would like to add to the above statements is that we must teach our children what the Christians did to our folk in ancient times. Once they are old enough we should not hold back the truth of what happened to our religion, and our ancestors. But we should do it in a way that fosters pride in our martyrs, heroes and even the common folk who lived through that horrible event, and not in a way that builds hate against other modern day religions. Our children are our future, and the future of our religion rests in their hands. Teach them well, and our religion will flourish and return to its former glory. Teach them poorly, and we will dishonor the Gods, and the memories of our ancestors who died for our Gods and our religion .
Go with Odin's wisdom, Freyja' s love, and Thor's protection !