Is Areolae Reduction Good 3 Years Before Getting Pregnant?

Probably not.
An areolar reduction can be done by itself or as part of either a Breast Lift (Mastopexy) or a Breast Reduction (read link below to understand similarities and differences). With Pregnancy the breast will grow and stretch the entire skin envelope, including the areola. Any tightening of the areola and or of the skin envelope will be affected - the areola will be stretched as will be the skin envelope.
Dr. P. Aldea

In my opinion, this would not be a good idea.  Isolated areola reduction without a lift or reduction of the entire breast is exceptionally rare anyway.  I think whatever you might gain would potentially lost be the stretching of the breasts during pregnancy or breast feeding.