I would suggest pre-seed.Everyone here swears by it & its sperm friendly =)
There have been many studies done on what influences sperm survival. And most studies show that saliva can have a negative effect on sperm. If he has enough sperms then it's unlikely to make a major difference, but if he has a low sperm count then you need every single sperm.
Saliva throws off the delicate ph balance and introduces outside bacteria. These things kill sperm - they aren't terribly hardy to begin with. Regular lubricants do the same thing - they are too thick for the sperm to swim through and the ph balance is all wrong.