I think you’d be better off investing the time you’d have worked to pay for FB ads, etc into some good business cards and going to businesses. Leave a card (or flier) with receptionists at community centers, centers specializing in counseling/ psychotherapy, occupational therapists, physical therapists specializing in children are just a few I can think of off the top of my head. There are many LMFTs that are specializing in families that have children with special needs now, especially with further awareness of SPD and ASD. Pediatric offices sometimes have bulletin boards that you can post business cards on.
AND, I think an even more effective way to use FB instead of paid advertising (and this part is completely free but does require a little more FB legwork from you but does NOT require updating a page with new material) is find your local B/S/T pages, join the group and then post a link to your portfolio and site with a quick blurb about what you do. You’ll get a lot of immediate contact from that one post.