I had my first at 34, my 2nd at 38, and will be 41 when my next is due. As for how differently you'll be treated, it really depends on the practice. My ob/gyn for #2 (when I was 38), didn't treat me any different from an 18 year old and was very clear that he wouldn't be treating me any different. But he had his own, private practice--no other mds or cnms--and could do that. Group practices tend to be a little different, I think, because they follow guidelines that are acceptable to everyone in the practice. But, really, at 35, particularly since you've already had kids, you shouldn't expect any difference. You might be offered some extra testing, but that's most likely it.
I will also be 39 or 40 with this child and I'm not expecting anything different than with my last two (which I had at 35 and 37). I'm not in the US, but it seems that docs/midwives/whatever are a lot more chill nowadays about "older" women having kids. I raised the idea of being a bit old for a third child with my doctor before we started TTC, and she just stared at me and said "you're still young" - I am sure she was joking a bit, but not totally. It also may depend how much trouble you have had conceiving, and your health to start with, more than specifically your age, at least that is my understanding of care for my location. They will probably discuss testing more thoroughly with you, but hopefully won't be forced on you. My docs suggested weighing the pros and cons of testing very carefully, and they certainly weren't pushing me to have testing. While blood testing is available here, I would have to fly 3 hours to have nuchal translucency testing anyway (on my own dime), so that seems pretty unlikely!