Dora,
Since you are asking for advice I will offer my gut reaction to your first time carnival. I think that you are being a bit too aggressive in the things you are having at your first time carnival. If you had been having carnivals for 5 years I would say "Go for It", but my advice would be to scale it down a bit. Here are my reasons I say this. (I am offering this advice through my school's perspective.)
First, you need a lot of parent volunteers. Unless you are having your carnival for only 1 hour, you will need each two or three shifts of people manning each booth. And if you serve foor, that is a huge labor pool that you need to serve and prepare food. So you need to have a ton of parents willing to help out.
The problem I would have at our school with the events you picked is from a parent's perspective of helping out they are not very "volunteer friendly". It sounds stupid, but let me give you the excuses you are going to get.
Dunk Tank - They are afraid that they might get wet.
Nail and Hair Coloring - Very few parents are going to be willing to do something creative like this. They are afraid that they aren't good enough or creative enough to do nails, hair or even face painting. We have had to hire people to do our crazy hair booth, just because it takes a special talent and type of person.
Karaoke Machine - Anything electronic or technical like a karaoke machine also scares people off. It may be as easy as a radio to run, but people will have this fear of this electronic machine.
Second - The biggest obstacle with a carnival is literally setting up the carnival. Unless it is on a Saturday, you usually get into the gym or school an hour or two before the carnival, and then it is a mad scramble to get it all set up. And once again the booths you have involve a little more set up than just simple carnival games. For example the dunk tank sounds easy, but it will take one volunteer the whole set up time getting the dunk tank set up and filled with water. The crazy hair booth is also a little more involved in getting set up. The biggest hassle getting set up will be the food, you need to get it set up and prepared.
Third - I think you need more simple table games or carnival games. Simple games such as bean bag toss, Plinko, ring toss, basketball shot, duck pond, fishing pond etc sound pretty lame, but the kids love doing them and winning worthless trinkets as prizes. It also gives kids activities to do. One problem I see with your events is they are great crowd pleasers, which can be good or bad. The dunk tank will have a crowd watching, the karaoke will have a crowd watching, the crazy hair will have a crowd watching. The problem is none of those events can handle a lot of people per hour, so a lot of kids will get bored because they are only watching, not participating. They would rather do a simple carnival game that sit and watch other people doing things. I use the rule of thumb of having a the same number of simple carnival games as you have classrooms.
Also, parents will volunteer much more readily for a bean bag toss game than the crazy hair. Most of the games are ageless, so parents are more familiar with them and will volunteer.
Fourth, DO NOT PLAN ON YOURSELF OR THE OTHER TWO KEY ORGANIZERS HELPING OUT AT ANY BOOTH. You and the other planners will be busy putting out the 500 or so problems that are going to appear. You will not have a spare minute to man a booth or cook food. You will be finding the janitor to unlock the dock doors for the food delivery person, you will be finding a hose to fill the dunk tank, you will always be looking for tape or a marker, you will need to find someone to run and get forks which were somehow missed.
Here are my honest suggestions.
1.Scale down your "marquee" events to a dunk tank and crazy nails at first. Those are the going to be the most popular, so plan on having them fully staffed. The dunk tank will suit the boys, the crazy nail will suit the girls.
2. Throw in a cake walk, even if it is for cookies or candy bar. You can have 20 spots and they will always be filled.
3. Plan on 10-15 more simple carnival games with worthless trinkets as prizes.
4. Make sure you start getting volunteers extremely early. That might be your biggest battle.
5. If you can have White Castle handle the food, do it. Food is a huge hassle, so if you can farm that out it will help greatly.
Anyway, just my ideas. I figured since it is your first carnival you might want to start off with smaller plans or it will totally engulf you.
Thanks for listening.