Buy Bright, Long Burn Time Sparklers with Low Smoke Emission
That's fancy talk for saying if it smokes like a chimney, the photos will be a hazy mess. And if the burn time is only 45 seconds, you may not have the whole line lit before the the first ones flame out. My best advice is to test them at home before using them at the wedding.
Set Aside 20-30 Minutes
Yes, the DJ can make an announcement to your 250 wedding guests to relocate for the sparkler exit, but it's a bit like herding cats. Assign two people to be the shepherds. Their job is to organize everyone.
Make a W-I-D-E Aisle
Seems logical. Sparklers can burn at 2,000 degrees Fahrenheit. Sending a bride in a long veil, with copious amounts of hairspray and a fluffy dress with a train through a narrow tunnel of sparking flames is maybe not a great idea.
2 Lighters + 2 Shephards = every 4th Sparkler
It would take too long to light each Sparkler individually. So have your helpers each take one side of the aisle, and then they will light the sparkler of every fourth guest. The Guests will then help light the sparklers in between them.
Walk, Don't Run
If it were me, I would totally duck and run too. Depending on the ambient light conditions, focusing may be tricky and running makes it more challenging. If you really want to make me a happy photographer, stop about 5 guests short of the end and give her a dip and a slow kiss.