Don't approach this like a major holiday event for 25 people. Set short and long range goals. Build in an extra time for a ten minute break every hour. Set a timer for planned breaks and again to be refocussed. 3 consecutive Saturday mornings from 9am to 12noon.
Some people find it more productive to select a consistent time.
Try to make adjustments only when necessary. You're almost there. This may motivate you and help avoid interruptions and distractions. Make this contract sacred like your kids playdates or your husbands golf game. Your determinations will teach household members about the accomplishment of completing a task successfully.