Maple bats in particular were once known (circa 2008) to potentially shatter in a way that resulted in many sharp edges, sometimes creating more dangerous projectiles when a bat broke. Maple bat manufacture evolved significantly, in cooperation with Major League Baseball, paying special attention to grain slope, and including an ink spot test to confirm safest wood grain orientation.
This is the drill we ran all through high school. It is the most time effective and skill intensive way to warm up a team, but your boys must be able to play catch! Fungo-ers stand in the "fungoe circles" that any good field has (and if it doesn't, you know where they're supposed to be - just outside of the home-plate dirt circle, towards the dugouts). The catch to this method is this - you have two first basemen, allowing both sides of the infield to throw across. Herein lies the only danger - one of the firstbasemen has a lengthy throw back to a shagger, so caution must be excersized (a catcher with a good head on his shoulders really helps).