That's a 2 stop push then if it defaults to 100. if your compact has exposure compensation use it, most basic ones will have a button for 2 stop over exposure for things such as backlit subjects (sunsets with people in foreground).
Lead X-ray bags come in different grades, basic are lead lined plastic, best are multilayer lead woven into heavy ballistic style nylon. Manufactures grade them for protection from 200-800 speed films usually. This is for carry on protection only. Check in luggage or mail may get exposed to much higher levels which any bag can't protect against. Not alll mail is xrayed though and slow speeds will be affected less. What if a real worry is hand inspection.