that's exactly the point, hilda. everyone's decision is a valid one.
apols for getting wound up by dolfrog - it was really a defensive mechanism as i didn't want your decision to be in any way affected by criticism of working parents - there's enough of that in rl, even for mothers of nt children. and it seemed as though dolfrog had swallowed the ridiculous notion that sn parents are in some way special, and if we aren't, we need to work extraordinarily hard to get that way, with a good heap of guilt thrown on top.
as far as my personal experience goes, i kicked off with nanny's upthread as it was mentioned in the op, and because it was by the far the most practical 'gold standard' solution, but of course there are financial implications.
i've pretty much been through most work/ care combinations. dd2 has cerebral palsy (we were told she wouldn't walk or talk v early etc, although she now does) and is the youngest of three - so as well as childcare for her, we've had to take into account her older siblings.
i mostly sahmed for the first two years of her life (in that i worked weekends away from home, when dh could have the kids), and have since been through most options! i don't have a 'career' per se. we travel a lot with dh's work and so i have to be quite opportunistic as far as my own work - so sometimes i get the opportunity to do a 6mo ft contract, sometimes i've worked pt for a couple of years, sometimes i've combined study and a couple of jobs etc etc. however, when working ft, the nanny solution provides the stability for the kids and the flexibility that their schedules (inc therapy appts etc etc) demand. i've also used ft nursery for dd2 (8am-6pm) and then school and after-school club (she was funded 1-1 support for the after-school club by the lea as she was statemented with ft 1-1 in school). the other kids have used after-school clubs and child minders. just recently i've started looking for a childminder that will take them all as we've moved and i'm job hunting again. 
it's my judgement that she can cope with a childminder now - the one we trialled last week has a house full of snakes, turtles, and frogs. dd2 was enthralled and spent about an hour watching a turtle.
as well as working, i've found that parents of kids with sn often have the greatest impact on service provision, and so by default you can become a disability rights activist... often the only people to kick off new provision are parents themselves - and so it's a case of 'if i don't do it, no-one will', and so the demands on your time increase. you then aren't doing it just for your child, but for the rest of the kids that might benefit from accessing the service.
ultimately, you have to look at your own circumstances and judge what's right for your family. and money does have to come into it at some point. and whilst i agree absolutely that the majority of society should be taxed and fund the most vulnerable, it is your personal decision whether this would be the right choice for your family (in terms of both income, and care needs).
dd2 has loved and adored her carers - we've employed two nannys at different times, and the nursery staff were brilliant. in fact, i did have to ask nursery to remind the 1-1 that she was there to facilitate dd2's independence and help her access the activities, rather than provide such a comfortable cushion that she was sheltered from her peer group. because we move so often, she changes both therapists and school etc every year or two, so as her parents we are the constant source of love and support anyway. whilst she might make strong bonds with 'outside' care, they are there as facilitators, not parenting her.
so again, it's all very personal. but don't base your decision on my rambling , or anyone else's .
no decision is set in stone - flexibility is the key. if you go back to work for a year, or six months, or even three, and decide it isn't working for your family, then that's a decision you can make then. or if you feel you need to give it another year and spend a bit more time at home, then that's ok too. no right or wrong answer at all. and no need to try and make lifelong plans - everyone's situation changes as we chug along.
what does dp/dh think? don't forget that it's possible that s/he might be able to alter their own work arrangements to take on more of the caring role. (as i said, for the first couple of years - and indeed later on - i worked weekends and left the kids with dh for days on end )
and again, apols for the earlier rants - i find 50yo men often like to tell younger women that their place is in the home, regardless of sn and context, and perhaps judged dolfrog's intentions incorrectly.
but don't let anyone tell you you're special! and never feel guilty for being an ordinary mum trying to do the best for her family! it's all any of us can do. 