Using a straw helped us teach our son (then 6) to swallow pills right down. It has something to do with the shape the mouth makes with a straw and sucking.
Here are some more strategies to try too. Ultimately, getting him to swallow pills would make life easier for all it sounds like.
Penny
ADDitude Community Moderator, Author & Mentor on Parenting ADHD, Mom to teen w/ ADHD, LDs, and autism