G.W.
I think it would be fine for you to bring your daughter. You could say she can "model" some of the outfits.
As far as the playgroup idea, Well, I can't speak for everyone but I know I would not pay $5-7 for my child to dress up for one hour. I'm sorry, that must not sound so good. But that is honest. You may have better luck telling the group, "I charge $75 per hour so the more kids you have come the cheaper it will be per child for your members." That way you know how much you'll be making regardless of how many kids show up. Also if you're going to charge the moms for the dress up I would make sure there are activities. If the kids are just gonna dress up, they could do that at home for free. Also try to realize that if you have activities/crafts while the kids are wearing the costumes, they may get spilled on or torn or ruined. That will cost you money to get them fixed or replaced. If you bring your stuff to playgroups, you may want to have 2 separate activities: one, dress-up. Then, two, activity time.
These are just my opinions. I hope I didn't offend you.