Sparkler send offs are always one of my favorites. If you are considering having one, there are several things to take into account.
1. The size of the sparkler. If it is too long, it will droop. If it is too short, it will go out before you get all of your photos. I prefer 20".
2. Where to have your guests stand. If they are too close to you there is a chance your veil, hair and dress might catch fire. If it they are too far, then the photos don't look good.
3. Where do you have the send off. Make sure you are paying attention to the type of ground you are going to set up at. You don't want to set up over dry grass, mulch or anything that could be ruined if sparks land on it.
4. How to light them. Have multiple lighters. I like the blow torch kind better than typical candle lighting ones. Start in the middle of the line and have the guests light their neighbors.
5. What do you do going down the line. Go through like you are leaving, but stop in the middle to kiss. If you wait to the end, then the lighting doesn't work as well.
6. What do you do when they burn out. Have a metal bucket of sand (preferred) or of water off to the side. When guests are done, have them place them in the bucket. If you use a plastic bucket, it could melt.
Have someone get your guests ready. It will literally be like herding cats....
You might have to light the sparklers before the end of the night. You need to make sure you have enough people to make it work and at the end of the night most of your guests might have left.
Make sure your photographer has plenty of time to adjust their camera before you light the sparklers. There is skill involved in getting a good sparkler shot and they will need to prepare.
DO NOT let kids or drunk people have them for the photo. Neither will understand what needs to be done and it becomes a safety issue.
Finally, hire a planner for your wedding. This is one of the many things you do not want to have to worry about going off without a hitch.