Milk allergy

Faith

My 2 and 3 year old recently did a food sensitivity test and both came back with results saying they were highly sensitive to cows milk. Luckily neither of them seem like they are in any kind of pain or discomfort ever, however they do both have always had rather hard and pebble like poops 💩. I’m sure this is a symptom of the milk sensitivity. So I am wondering if anyone had any suggestions on how to switch them over, and what I should switch them over to? Would lactose free be better, or should I totally change gears and go soy, or almond.. or even oat? Not sure what to do 😥