In simple terms, the risk posed by breaking a CFL bulb is much more like breaking 64 mercury thermometers. Does 64 broken thermometers in your child's room sound like "a very small amount of mercury"??
And if it's such a negligible risk, why does the EPA recommend these actions;
* Open a window or door to the outdoors and
leave the room
* Shut off the central forced-air heating/air conditioning
* Check with your local or state government about disposal requirements
* leave the heating and AC system shut off for several hours
* The next several times you vacuum, shut off the HVAC system, close the doors to other rooms, and open a window or door to the outside.
http://www.epa.gov/cfl/cflcleanup-detailed.html