The way that gets handled at my work is they count the blatant marketing as a Professional Development Hour towards keeping their PE's current. If you wait until AFTER the present ation to give out the goods (PDH Certificate), they tend to stick around.
Me, I don't need PDHs yet, so I am just there for the free lunch!! haha
You have this one the wrong way round - Having spent the last recession trying to sell to enginners - their way of appearing proactive was tio invite vendors in to lead a seminar (that was of course blatent marketing), eat the food and then, 10 mins into the prsentation "Oh I have meeting to go to . . . . . . ".
You were lucky if you didn't end up talking to yourself.