I'll start by saying that you are putting yourself in a no win situation. When you start burning disks for other people you have to realize that in any group of people you will find people with DVD players that range from top of the line to some old piece of crap they bought from a garage sale. Not all DVD players are alike. What plays in 1 may not play in another.
That said there are some things you can do to increase the odds of the DVDs working. Start by using -r disks... they were the first standard so the odds of them working in any range of DVD players your customers have should be slightly higher... especially since most DVD players that play +r also play -r but not all -r will play +r.
Next, I would suggest you get a external burner and not rely on the mac book pros internal burner. While the MBP burner may work fine I've also found that when I burn the same thing using the same brand of disk that I can sometimes get coaster from the Mac's internal drive (though they often still work on the Mac's drive they just don't work on the home player)...
As for brands, as long as you stick with named brands you should be okay. But never assume the named brands are 100%, I once had a 50 disk pack and after 4 coasters started looking at them closely and found that each one was defective.
Lastly, it might not be the most popular thing to say, but I tend to get more consistent results using Nero in windows than I do with any burning program for the Mac OS.