I would recommend, though, since you will (hopefully) be a repeat source of site suggestions, that you remember your reputation.
I don't know what kind of clients you have (and the principle applies no matter what kind they are). But sometimes you may need to tell a client, "without a site you don't have a real business, and so from the OD perspective, you can't have a site ABOUT your business" or "the OD has no control over how many sites you create for the various product lines in your business, but they will only list one site about your business. Let's make sure it's obvious (to surfers) which site is the main home page for the business as a whole."
Some clients may not like that -- but better to run the risk of telling someone the truth, than to run the risk of having a reputation for telling the ODP sites are listable, when they aren't.
So ... know the ODP EDITORS' guidelines -- they are public. And (please) suggest all the listable sites that you know about -- whether they are your clients or not, your help to the ODP is (eventually) appreciated.
Oh, ... make sure you don't make any promises about times or schedules of ODP listings to the clients. Even we can't make such promises. And again, it's a matter of getting a reputation for telling the truth.