I have the same situation, full middle name on DL and PP, only middle initial or sometimes nothing on the ticket, and never had a problem either, so I'm not really bothered.

I'm only concerned in this case because the travelers in question (family) will all be using their foreign passports as ID and are all from south Asia, and I want to minimize "opportunities" for TSA screeners at BWI to exercise "vigilance" in search of The Big Catch. I suppose worst case would be an extra SSSS for some of them. At least I'll be with them to help mitigate any issues.

Guess I shouldn't worry about it too much, it's just that I've heard too many negative things about TSA at BWI, but haven't personally flown out of there in a long time.