Hockey tables come in different sizes to suit different target markets. If the players will 99 percent of the time be kids, you have to take their size into account when buying the table. Make sure it's small enough so that they will be able to easily reach all parts of the table.
The standard size used for hockey tables used in professional tournaments is 50 inches wide and 90 inches long. If you want to attract the neighborhood's top players to your games room, you might want to give this size serious consideration. Make sure that you have a room size of at least 10 feet by 7 feet to work with though.
Also, consider the size of the room before you buy the biggest hockey table out there. Remember that it's not good enough for the table to merely fit into the room, you should also allow a few extra feet of open space on each side, so players can move around easily.
If space is very limited, everything is not lost. There are nowadays a variety of tabletop air hockey games on the market that require only a flat surface of about 40 inches long.