No kids here, but I have been a volunteer little league coach for the last four years, starting with t-ball. The most important thing is that the kids have fun. Encouragement is key. Be a little goofy if you have to. At age five, all the kids want to do is hit, and they occasionally do just that! When they're in the field, some of them are building sandcastles, some are talking to their buddies, and a few are actually paying attention to the game. A big thrill when I coached t-ball was when they actually got an opposing payer out.
I cannot stress enough: Make sure he is having fun. Winning and losing are irrelavant at his age (we didn't keep score until this year, and the kids are now 8-10 years old, and I think I liked the old way better.)
As a coach, the second biggest thrill is when the parents request that their kid be assigned to your team the following year. Makes you feel like you did something right.
The biggest thrill is seeing former players on the field the next year, and having them be happy to see you, and knowing that you might have had a small part in them deciding to play another season.
Just happened Saturday, as a matter of fact.
Have fun; I know you will.
-Jim