Hi-- I am a parent of a 2E boy with Asperger's, now 8. Your mileage may vary from ours-- girls with Asperger's are less-charted territory. There are no easy answers.

We sent DS to K on time, on the young end of his class (summer bday), because he was so far ahead academically that we couldn't imagine redshirting him. He had a truly awful year in K, a moderately awful year in 1, and a better but still taxing year in 2. I don't want to scare you, but DS's K year included lots of meltdowns, inability to fit in, difficulty following the rules, and failure to participate, pay attention, or even physically be in the circle at circle time. This stuff can be worked through (ABA is great), but it's hard and takes time. I assure you that things are much, much better now for DS.

In our district, K looks like grade 1 in terms of the expectations for sitting on the floor in a group, listening, hand-raising, following directions-- a big step up in social expectations from preschool, which is precisely what kids with autism struggle with the most. What our DS needed was something with advanced content and still having explicit teaching of school-related social skills like you get in preschool-- which doesn't exist here.

I still don't know whether it would have been better to redshirt him and then gradeskip later, or not. The school has been accommodating the 2E better lately as they have gotten to know his needs firsthand, giving him teachers who can deal with differentiated instruction and allowing him to have appropriately accelerated math. This has been a big process, challenging and consuming for us as advocates.

Honestly, if you can give them another year of ABA and part-day preschool, they may enter elementary school better equipped and more ready. It is easier to develop good play skills in preschool than in K, and play skills are likely to come hard to your kids. On the other hand, if your school district is ready to give them good help in the classroom, you may want to enroll them, and then let them repeat K if you find they're not ready for the full day of grade 1. You might want to talk with the school principal and the district special ed people to see what's actually available. What I would not do, given my experience, is put them unsupported in the kindergarten classroom and expect them to do well.

(The district is responsible for giving them services already from age 3, did you know? So you could potentially keep them out of K and still get help, possibly a preschool program more targeted to their particular needs.)

Another thing about autism that may be relevant here is that some deficits show up later: while the early grades play to our kids' strengths in rote learning and categorizing information, once the shift is toward critical thinking, reading comprehension, and so on, often they fall behind. We are finding that our DS comprehends fiction only a little above grade level even though he decodes and comprehends nonfiction at college level-- that kind of unevenness becomes more manifest as they get older. It is sometimes better for them not to be tied up in how "smart" they are, because when they hit grade 4 and suddenly don't feel "smart" any more, it can be a terrible blow to them. Not that this should necessarily affect your redshirting choice now, but it could become a factor in your long-term planning.

You may find this website useful: it has a very nice discussion forum about issues particular to autism, with lots of experienced parents. Redshirting has certainly been a topic over there, with pros and cons weighed carefully.
http://www.aspergersyndrome.org/Home.aspx

On the issue of labeling: I am strongly pro-IEP. It gives your children legal rights and protections that they really need. Those protections may give you trouble with teachers who are unwilling to deal with "different," but you can advocate for your kids not to be placed with that kind of teacher-- and the IEP gives you power to call meetings and solve problems with the school staff whenever you need to. We bring ABA staff to those meetings, and that is helping the school learn to "get" 2E.

It's a process. But if you aren't frank with the school about what the problems are, your kids definitely won't have the support they need to be successful, which means they'll be facing more problems on a daily basis. And it's surely better for them to go into school labeled as "autistic" than as "poorly behaved" or "problem children."

Feel free to PM me if you want more info. I could write a book.

HTH,
DeeDee