I've heard that extra zinc in the mans diet really helps sperm. Not sure about motility wise but I know I've read and heard that before!
The fertility books in my little library point to Vitamin C as a key nutrient to sperm motility. There's the obvious pill supplement he can take, but there's plenty of veggies and fruits to meet the daily needs. Vitamin A is another good nutrient for motility, too.
I read about garlic and korean ginseng being good for sperm production and motility.
I know this is very late, but thanks for all the info!