Team parties are generally held at the end of the season, to celebrate a successful run, to give out awards, or just to socialize. However, team parties held at the beginning of the season are an even more useful tool to coalesce the team into one strong unit.
Hold an informal pizza party or picnic within the first two weeks of the the season. This is best held in an informal setting, such as a player's home or a park. While the kids are having fun playing with one another and bonding, the coaches can meet with the parents, discuss rules, philosophies and goals, and set proper expectations. In addition, the parents can meet one another, make the connection as to which kid belongs with which parent, and even set up car pools.
Without a doubt, this style of team party does more for the benefit of a team than any other activity. Just keep it casual and have fun!