Tell your kids to stop chewing on the walls.
They sell simple kits that you can use to test the old paint to see if it is infact lead based and I recommend that to everyone who thinks it may be.
I have a buddy who was told his house was lead based and that he had to hire a pro to have it removed by the inspector and was about to pull the trigger until someone said to test it first. Well he tested it and was not lead based. Saved him a great deal of cash.
Here is a link to the Depot's test kit.