I often white hat pee-wee games and I have found several things to be critical.
Firstly, make sure all three officials are on the same page. If the league has any special rules, make sure that you all agree on what should be called and what should not. As with any other level, perhaps more, consistency is key, so it is important that each official flags the same fouls. For example, in the league I work we have a no blitzing rule. Typically I work with the same officials each week, but anytime I get a new official, I go over what we would like to see called and not. Consistency from week to week is critical in garnering the respect of the coaches that you see each week.
Also important, as mentioned by several others, is to always take whatever time necessary to get it right. Get all the necessary information from the other officials and give good preliminary and final signals. I have seen many white hats not do this in pee-wee leagues and it leaves the coaches, fans, and players confused what happened.
One thing I believe in for pee-wees is offering the coaches more explanation on difficult or strange plays/rulings. This is, of course, only when the coach is reasonable. Most coaches do not know the rules inside and out and youth league coaches most often know them far less. In my experience over the past few years, coaches will listen and appreciate the explanation. Do not let it hold up the game, but tell them you will explain fully later and catch them on the next down time, perhaps after a score or change of possession. As always, you will have the unruly coaches and they should be managed accordingly.
One person mentioned letting the coaches ask questions. During the coin toss, I always ask the players if they have any questions. Then, I ask the coaches if they have any questions. (we always have one coach at the toss) During the early part of the season they usually have questions and this gets them answered.
Lastly, you are likely putting too much pressure on yourself. Handle it like any other game and you will do fine. Good Luck!