Hi Nat, I can understand that your ex doesn't want to involve lawyers until an agreement is reached. It is certainly cheaper on legal fees in you have in place an informal agreement before you engage a lawyer. However, it will be difficult for you to know whether the deal being offered by him is a fair one without you first consulting a lawyer.
Has the registration on the cars been transferred to your ex?
I assume it has, in which case the cars will form part of the divisible property pool. However, including them in the divisible property pool may or may not be to your benefit. If the cars were inherited a long time before separation they will be treated like all other joint property. If, on the other hand, they were inherited toward the end of the relationship, or after separation, your ex might successfully argue that the cars form a separate property pool to which he is entitled to the value of all, or nearly all, of it. Hope this makes sense.