The ideal age according to medical science is during a woman's prime- 20's and early 30's, after 35 doctor's say your eggs aren't as viable and your risk of miscarrige is greater. History shows that women are having childen later in life and the children are just as healthy as children conceived by women in there 20's. Medical science has come so far that women don't have to worry if they are to old to have children so to speak, if you take care of yourself, get the proper prenatal care you can and will have healthy children. Stop focusing on age soooo much especially if you are only in your 30's.
I personally think that the ideal age for a women to have her first baby completely depends on the women. I know for me, I waited until late 30's as that is what works best for DH and I. Its true that once over 35 some women can have a little more difficulty conceiving and possibly carrying, but there are lots of women who wait and do just fine. So yes, women from 34-35 can become pregnant, and lots do. There are no real extra precautions except that an OB or RE may suggest amnio as the rate of downs, etc. can increase a bit as we get older.
As for the sexually active part, women hit their "peak" in their 30's so no problem there!
34-35 is the perfect age... and women get more sexually active after age 30 :)