Hiking with a 20-month old

Does your son drink formula or cow milk? If cow milk you may want to look at NIDO's kinder drink they make, it is designed for toddlers to young kids. Not as rich as full fat NIDO full fat milk/easier to digest.
You can find this sometimes at Super Walmarts in the dry milk section or on Amazon.

If you do use say powdered instant dry milk, flavoring it is a big thing…otherwise it lacks in flavor!

I'll check out the Nido. My son drinks cow milk.

If you are going to be looking for the Nido at a walmart try looking the hispanic foods section. Thats where I found it at the local walmart, its not with the actual dry milk (all they had there was the non fat dehydrated milk)