We usually buy from our local base. Then, we always plan a no-park day for our arrival day. We go to Disney Springs to activate tickets at guest services there and then have dinner. Its been no hassle in my experience. Last time (Dec. '17), all the folks in our group handed me their magic bands, and I was able to activate them while they were shopping. Since you'd have 3 different groups technically, you'd probably need those three people to be there to activate and the rest can shop or hang out while you take their bands to guest services.
And, we also purchase the military discounted memory maker while activating bands at DS.