You can carry concealed as you normally do across state lines as long as the state you are going to has reciprocity. Ask your wife this, if carry across state lines is illegal, then what is the purpose of reciprocity?
If you are traveling to/through a state that does not have reciprocity, you can still carry/transport the handgun either in accordance with the state laws for the state you are physically located in, OR in accordance with Federal law below. The Federal law is merely an option, IF you choose to transport that firearm that way. For instance, in Washington, without a recognized carry permit, you can carry your loaded handgun in a holster so long as it remains visible (open carry), until you enter a vehicle, then the gun has to be unloaded.
Since the states you are traveling through/to have reciporicity you can continue to carry concealed, however, be aware that each state's laws you are currently located in will apply, so there may be different off limits areas.
Here is the Federal law which can be used an OPTION for transporting a firearm:
http://www.law.cornell.edu/uscode/18/usc_sec_18_00000926---A000-.html
Notwithstanding any other provision of any law or any rule or regulation of a State or any political subdivision thereof, any person who is not otherwise prohibited by this chapter from transporting, shipping, or receiving a firearm shall be entitled to transport a firearm for any lawful purpose from any place where he may lawfully possess and carry such firearm to any other place where he may lawfully possess and carry such firearm if, during such transportation the firearm is unloaded, and neither the firearm nor any ammunition being transported is readily accessible or is directly accessible from the passenger compartment of such transporting vehicle: Provided, That in the case of a vehicle without a compartment separate from the driver’s compartment the firearm or ammunition shall be contained in a locked container other than the glove compartment or console.