So you have one or two more cars you no longer need to use, but still you correctly think that it your vehicle may give more benefits for the sake of the public interests. Thus, you want to donate car to charity which, as you correctly assume also, will then be passed on to someone or any party or organization in need of most. This definitely is the best intention you could have and thus it does make out for the best deed you could perform. Knowing that you could do something to your society, though still at the lesser and smaller part of contributing, nonetheless this is a contribution after all: hence yes, you have set some best samples to the rest members of your society.
However, donating a car is not the same with giving your car just like that to some party or even organization. You have to make sure that your intention is all that worthy and thus you need to confirm that your deed is all put into a next good effort. That is why you need to find out to whom you are about to donate your car to. You cannot just give away your car to some certain committee and or organization without first looking at the how reliable that organization and or how significant their works to the society itself.
You have done your homework really, that is to say, you have been making some good and worthy effort in donating your car. Now, it is this committee and or organization homework to prove that they are, after all, equally worthy to receive your good deed. Ensuring that none of your good intentions and or deeds shall lie waste to your society (or worse, even benefit certain part of society which it shouldn’t!) will guarantee that all your donations pay back for your reputations and esteems.