My friend's son has Tourette Syndrome, and they used a combination of a pediatric neuropharmacologist to work with medications, and a behavioral therapist who specializes in kids with neurological issues. There are substitute behaviors that kids can learn to minimize the more annoying and disruptive tics. This is different than standard OT. You really want someone to teach additional skills but it's a bit of a specialization.
I think you should get a jump on this, not just because of his education and socialization and peace of mind, but because puberty can throw things into a new level of chaos, and you really want this well underway before he's 11 or 12. Hormones can increase the tics, and also interfere with finding the right medications and dosages - once you get it squared away, the tween or teen matures and grows, gains weight & height, and all bets are off, so you start over. If you have a good baseline, it's easier to make adjustments.
You might contact the Tourette Society and go to some programs, get on line support, network for professional practitioners, learn coping skills and support skills for your child, etc. My friend did a lot of this and it made her a much more effective advocate for her child. Education is power.
There is also a lot of of evidence for DHA, a fatty acid found in breast milk and essential for brain development and function. It's available in low quantities in some grocery store products but it's unclear what the sources of that are high quality enough or whether it's in an absorbable form. It can be obtained through patented products (patents on foods are very difficult to get, and mean that the product is proven safe, effective & unique) formulated by well-regarded food scientists. There is also some phenomenal work being done in epigenetics, which is repairing the damage done to the packaging around the genome/DNA. Improper gene "switching" (which genes in the cell turn on, which turn off) is one of the most heavily researched issues and linked to such factors as lifestyle choices, toxins, environmental influences (pollution, chemicals), diseases, stress and other factors. Epigenetic changes are a big cause of so many problems, including chronic diseases, the huge rise in behavioral and neurological and chemical problems (ADD, ADHD, learning/sensory issues, ODD, PDD-NOS, Asperger's, autism, severe allergies and so on). The good news is that there are nutritional, non-pharmaceutical steps that can be taken to restore the epigenome to its proper functioning. It's not messing with the DNA - it's getting the genes back to normal (after other factors have messed with them) so they can do their job. Again, education is power.
A multipronged approach might be something to look into.