You have 2 options to do the tax:
1) Getting ITIN for them, then fill joint 2008 tax return if time is OK. Declare your son as dependent. This is the most simple way to do it. You have no need to declare your hu*****and as dependent because of "joint".
2) File as single, applying ITIN at the same time, declare no one as dependent. After they get ITIN number, file another form to do Tax adjust, you will get refund.
You have multiple way to do it, the final result will be the same, the bottom line is everyone (your hu*****and and your son) counts if they have ITIN. But before they get ITIN, they don't count.