Put a micro switch under the wallet. Hook this switch up to lights and sirens at a loud volume. Check the suspects underwear
If you dont mind ruining your wallet, you can always lace it with diesel oil.
How much earlier do the sons get up? Might it not be worth the trouble to set your alarm a few minutes earlier? (then again, they could be getting up at 2am to pilfer your wallet)
Whatever you do, I hope you figure out who it is, and why they are taking it. Then again, you could always "get even" and take merchandise of the same value from his posessions (secretly, of course) - see how he likes to be thieved.