Working in a pre-school setting is a great way to accomplish this. For many, the pre-school years introduce an opportunity for students to interact with other children that were not raised in the same way, do not have the same socioeconomic status, and/or are not of the same race, ethnicity, or religion for the first time in their lives. For this reason, a pre-school setting is a great way to work within the field of child therapy without working as a true child therapist.
You can also explore opportunities as a Registered Behavioral Technician. There are many organizations where you can work as an RBT and interact closely with children on the spectrum. This is a field closely related to child therapy but with less schooling and a narrowed-in focus on Autism.
You could also look into nannying full time. This gives you the opportunity to build close relationships over time with one or more children in a comfortable setting. You learn about their development and their understanding of the world around them through full emersion into their day to day lives. You can typically find live-in positions for this which can be cost efficient and conducive to your goals of full emersion.
I would definitely recommend teaching. The formative years of a human being are crucial. And contact with children should always be precursored with training and preparation for the immense responsibility it entails. If you really want to have a positive effect on society and get immense gratification at the same time, the work put into being a good educator will go a long way. There's nothing quite like a successful former student telling you that you changed their life. Trust me on this. Many of society's problems could be helped or eliminated by raising good people.