Hi Sarah,
I would use the Dr. Ohhira’s. It is safe for infants and your son is 17 months anyway, so no problem. Muscle test first to be sure his body accepts. You can do surrogate testing (I teach this in the muscle testing video).
Keep a good eye on his behavioral changes over the next few days and if he shows problematic signs in behaviors or physically such as extreme fatigue or flu-like symptoms, just wait a day in between and then begin again. Better yet, muscle test to see if he can have one per day, or one every other day, or one every two days, etc to begin. I like to give them at night before bed. The lesser amount of food in the stomach also helps the probiotic to be able to work a it better. Be sure to journal. If you see signs of die of (the physical and behavioral changes noted above) then the elixir from Get Healthy Again called “toxin eliminator” can be very helpful.