If you have one of those cable locks that goes through the firearm's slide or cylinder, you should use that as well: the more difficult it would be to load & use the gun, the weaker any possible case against you if it were found, stolen, or otherwise caused a problem.
When we drive through Illinois, both guns will have those locks in place, they'll be in a locked box in Elwood's trunk*, and the ammo & mags will be in a different bag.
*Yes, I named my cop car "Elwood." Wouldn't you?
If you don't have such locks, I'm sure someone up here would lend you theirs. (We'll be using ours). They're cheap, under $10 if you have time to order them online.