My DD is 10 and DD2 is 2 and we're having our third. I still get asked if it was "planned". (I am 35). My cousin is 39 having her first, so my rellies have definitely not said anything to me this time around! It's mainly friends. I still find it the strangest question I've ever heard, I would NEVER ask someone...
35 is not old to be having your third. 31 is the average age for first babies these days, so you're well in the "average" age range.
I think it's wonderful, and I think you're sensible, you'll have two helpers now!!! Funnily enough I know someone having her third and her two are 10 and 8!! Not sure why she has the gap, but again, I think it's wonderful!! And Im all for gaps!! xo