I think that the more you know the better you will be. Group training is different than one on one, sometimes it’s not be easily transferred.
I would recommend a group exercise leader certification from ACE or ACSM – both nationally accredited organizations which does matter!
It looks good on your credentials and it’s important to be as educated as you possibly can.
It depends on how comfortable the trainer feels about running group/boot camp classes. I personally don’t have any certification as a ‘group’ instructor, but I have been running boot camps for 6 years now. I have been and instructor for police SWAT units for a few years, which involves instruction of a large number of participants in each class, so instructing group classes and boot camps was not a difficult transition for me. But that’s me. Keep in mind that you’ll have to multitask (continually making the class format interesting and challenging, as well as correcting and/or modifying exercises for multiple clients at once). If you feel comfortable teaching boot camps then maybe you should give it a try and see how it goes. Better yet—before you start offering your own classes, maybe you could sub or work a few hours for someone who is already offering boot camp classes to see if this is something you want to get into. Or you can do it the way I did it—start training smaller groups (3-5) and when you get comfortable with that number, add more participants until you get used to training larger groups. Usually 10 participants per instructor is a good number, which helps you maintain control and make sure you give everyone a fair amount of attention and instruction.
I hope this helps.
I think there are overlapping skill sets, but also different needs of coaching a client individually vs. coaching a group of people. A group certification would be helpful in learning the differences between the two and provide you with information on how to motivate, educate and cue a group.
Is it a necessity? No. Helpful, educational and informative? Yes.