I told DS when he was eight, when he was first undergoing assessment (it was clear to me he had AS even though we didn't get the written dx until he was 9). I used a variety of books to help him, one was 'Can I tell you about Asperger Syndrome' and 'The Curious Incident of the Dog in the Night Time' (actually that was not the best choice for DS as DS found it hard to relate to the main character). I found some websites listing famous people on the spectrum (am actually a bit
about some as many were never officially dx and there is some controversy about them) - but for the purposes of boosting DS's self-esteem, they helped him view AS in a positive light. There are more books and media examples I think now that have emerged even in the past few years.
I think it is better, the earlier you tell them. DS is 14 now and is very comfortable with his dx. He goes to a specialist AS school now, which really helps as it normalises his issues and he can see that there is a broad range of AS. Some students have more difficulties than him in some areas, but others have strengths that most people wouldn't think possible with AS.
I didn't try to downplay it though, as DS's issues are obviously quite severe to need a specialist school, and it's a lifelong condition, as well as a disability - I think it's important that they recognise it as such so they can develop the tools to self-advocate. It's not just 'being different' - like being left-handed - it's being different in a way that has a ?substantial? and ?long-term? negative effect on your ability to do normal daily activities.
I think it can be most helpful for dc to come into contact with other young people on the spectrum, so they don't feel they are the only one. Even if your DD isn't a candidate for an AS school, they may be able to access a special needs play service through Short Breaks, or you might be able to meet other parents through local support groups and arrange a playdate.
I hope your DD is getting the support she needs educationally - that was one of our biggest battles, and also getting DLA and respite.