We encourage you to send your son a letter while he is in camp. Beware that mail service to camp can be quite slow. You may want to prepare your mail in advance and give it to your son's Scoutmaster prior to their departure with a note on your desired delivery date.
Here's the address for sending mail to your son:
Your son's name, Troop #________
Camp Lewallen
Campsite ____________ (see your Scoutmaster for the campsite name)
HC1 Box1955
Silva, MO 63964