I would choose therapy over nursing. Therapy gets way more autonomy and better hours. If you want to work directly with folks, you may want to try for Physical Therapy or Occupational Therapy. Those, however, because of degree inflation are now Master's Degrees and are pretty competitive to get into. However, there are 2 year programs in both OT and PT that will get you in the field and pays comparable (if not a bit more) to RN-AAS. Check commuity colleges if you go this route (PTA/OTA). Then take the program then bridge over to MS PT or MS OT. OT/PT do work most of the areas you say you would love, including pediatrics and phych.
Now... about CNA. I am a CNA currently. I have a love/hate relatioship with it. True, you help out tons of folks. But, in my experience, the "help folks out" is sometimes more along the lines of a room service for pee/poo removal, food, and fix the TV kind of way. A CNA does get good experience towards nursing. As a therapist OR nurse, it will help you through school for the mere fact pee and poo will not bug you and you will be already familiar with how people behave with mental problems and you will not freak out. Problem is, without experience you may end up working at, shall we say, not as good facilities. This is even if you say you are going to school. In fact, some managers do not like those going to school because if you are you may be tired or less likely to be as "dedicated". You may find yourself heavily overworked, put up with snide remarks, demeaning treatment, and be a dime a dozen. Now as a therapist, you can be firm with people. But as a CNA, one complaint will earn you a trip into a DoNs office or unemployment.
Myself, I chose COTA. I still do CNA, but I can not wait. The difference between nursing and therapy is this: Nursing is DEPENDENCE and waitering, Therapy is INDEPENDENCE and teaching!
Hope that helps and gives you other options.