Well dead batteries can do weird things. But it's a dealer right? Both these things produce codes that can be read in the service dept. They can also be reset not to come on again until later. What kind of warranty are they offering. If they will sell it "certified" you can get repairs at any dealer later. If they seem sleazy to you it might be a good way to go.
The airbag light will get set if the battery voltage drops below 9V but the airbag light and CEL light are not linked. The van may have to seperate problems.
You may want to get a CARFAX report on this van if you are still interested in getting it. It may be the best $20 you spend and you may discover some history that your not being told by the dealer.