This is a tough one, and best worked out locally. Has he shown any interest in games like Dungeons and Dragons or WarHammer? No faires, but there are elves and goblins and orcs. The advantage with either of those is that you may be able to find small game stores that organize events, or other kids at school who play them.
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Mom to an amazing young adult AS son, plus an also amazing non-AS daughter. Most likely part of the "Broader Autism Phenotype" (some traits).