What i do with my lot is simular to Mel..

(and hey, its not bribing, its teaching them patience.. so I tell myself!!!)

Set up something fun, just before his nap time. Morning tea for 2, playdough, paint etc.... tell DS1 its STRICTLY for mummy and DS1 when DS2 is asleep. If he wakes bubba up, we cant have it.

But you have to stick to it. If he wakes up bubba deliberatly, get rid of it, and explain why.
When he is nice and quiet, he will learn he and mummy get some fun stuff together!!!

The key is be consistant. If you give in and let him have it regardles he'll learn he gets it either way, so no need to behave.......... but if only gets for being good and quiet, its a nice reward!

Be warned though, tantrums could follow when he realises the reward disappears when he plays up!!!!

Just one suggestion babe, good luck!!!