Part III concerns the Boomers.
Head to the Nellis Airforce base to the northeast of Freeport. You may either complete Volare!, or defeat the Boomers in combat. If you with to help the Boomers, you have to obtain Idolized fame; the easiest way to do this is to complete quests Ant Misbehavin', Sunshing Boogie, Young Hearts, or find other ways to gain favor with the boomers.
When completed by either option, return to Mr. House and advise him of the deed.
When you complete this section of the quest, you will be alerted in your Pip-Bot that you are risking infamy through quest entries "Don't Tread on the Bear!" and "Beware the Wrath of Caesar!". Continuing along the Mr. House quest line will make both of those factions hostile.