Antibiotics are devastating to the gut ecology and it needs to be restored. Probiotics are exactly what he needs and yes in the form of cultured foods is best.
Also you could make him some bone broths, basically homemade chicken soup, just cooked at very low temp for 24 hrs or more and everything strained out of it when its done. This is very soothing and health to the gut lining. No spices but a good air dried mineral salt and but organic. Its delicious. Let me know if you want a specific recipe.
Even if his symptoms are gone I would recommend this, here are some great sites http://gapsguide.com
