Well, here’s a productive thread. 
Yes, I had quite a bit of experience with this on my hike. I live in Maine and belong to an outdoor club so there were quite a few people that wanted to hike with me, esp. when I got closer to home.
What I like to advise when this question comes up, is this: it’s easier if the folks coming out to hike not have a fixed section or place they want to meet you. iow, they have to schedule around you, that’s just the way it works. It CAN disrupt your rhythm, it will more than likely make you slow down and lose your friends for a bit, but it is fun to show your friends and family what this hiking (thru-) thing is all about.
I had a girlfriend fly out from UT and hike the Shennies with me, a few weeks before she picked a date and called the ATC who recommended she fly to Dulles vs. BWI and hooked her up with a shuttler. It all worked out great. Most importantly, don’t let them get you involved in their plans. They’re going to have to figure out their A==>B hike with you and how to arrange that, you can’t be worrying about it at town stops. Use the ATC and local clubs and their shuttle lists.
Another friend met me in Harper’s Ferry and walked to the Doyle with me for a week. That was a great time, he’s one of my bping buddies and knew what to bring and was in decent shape so could do the 15-20s a day and we didn’t lose my group. We had a ball. That’s a REALLY good section for people to hike - you have a state crossing/M-D line, Half Gallon Challenge, State parks with food and swimming, relatively easy terrain (the first part of PA is WONderful hiking) and interesting towns. Ending in Duncannon was a classic.
My brother came out to Cheshire to hike to Stratton with me. He wasn’t working at the time, so since this was the section he wanted to do he could be flexible on my schedule and also could drive there. He also paid for a shuttle.
Others did days or overnights in the Whites and Maine to meet me, specifically my husband who started being able to figure where I was within a few hours and would start hiking south to meet me.
Right now, before your hike, you just can’t predict. You might be one of the types that does 20+ milers day after day and finishes in 5 or less months. You might be like me who did 15-20s/100-105 mile weeks and finished in 6 months. You might spend time in DC, you might take the train to NYC, you might paint a house in VA for 3 weeks while you and your dog recoup. ?? These are just examples of how widely varying your schedule can become. I finshed 5 days shy of 6 mos with people that started 3 weeks ahead of me to 3-4 weeks after me.
Don’t shoot yourself in the foot and try to plan for them now. They’re the ones that have to be flexible, this is your hike and your schedule. The Outside World exists only for PO closures.
Have a wonderful hike Dave.
Bluebearee
GA==>ME 02
Bluebearee
Another thing, you’ll probably want to plan on tenting if you’ve got a group with you. A lot of thru-hikers will get annoyed when the whole shelter’s taken up with one group.