Pro tip. Have everyone get a 5 gallon bucket (or provide them yourself) put their names on them. That is the spot for bat, helmet, glove, hat, etc. So much easier than watching them all try to wrestle stuff into those backpacks that are too big for them. they are also relatively easy for the little kids to carry themselves. Tell the parents that your expectation is that the kids will load and carry the buckets to and from practice. Tell them that unless they are batting at the plate or the one the coach is working with on hitting at practice that the bat is supposed to be in the bucket at all times. Glove and hat go in bucket when your team is batting and helmet goes on in the dugout whether it's your turn to bat or not so that when someone ignores your bat in the bucket advice and take a swing in the dugout all of their melons are protected. You can buy the buckets for 3 bucks at Home Depot or on Amazon.
I second the "rotate everyone except for 1st base" advice. Only use the 2 or 3 kids who can actually catch the ball (or at least make a decent effort to catch) at 1st base. Pitcher is also spot that probably only has a 2 - 4 person rotation so they don't get hurt.
Avoid the temptation to just have the kids circle the bases on the inevitable train of errors that will happen on each and every play. Advance one base per hit unless it is hit to the outfield in which case a double is usually sufficient. The less you let the kids run per hit, the more hitters will get to come to the plate based on whatever your leagues run per inning limit is.
Is it strictly T-Ball or are there some coach pitches allowed / required before the tee? if coach pitching is part of the process make sure the players get plenty of practice doing that in the same way they will see it in the game.
It really can be a lot of fun!!