Well, you didn't leave yourself much time to prepare, plan, and execute a recruiting campaign, but I will help brainstorm a bit.
Now, I don't know what your area is like for competition, so I will be fairly general.
The first think I would think about is who those groups are. 5-8 and 14-18 year olds are pretty different in terms of what will attract them. 5-8 year olds are looking to have fun, to learn something new and cool. Their parents will also have to be sold on the idea and believe that your program will benefit their child. 14-18 year olds on the other hand will be in it more for the competition, the challenge, and for social reasons. And although the parents will still need to believe in your program to pay for it, the older group will be a bit more independent.
Get yourself in the community. Make yourself visible. It is always surprising to me how many people, even other cheerleaders, have no clue what all-star cheer is all about. It sounds ludicrous to me since my life is pretty much cheer, but its true. Other cheerleaders who have heard of all-stars often have distorted views on it. They think that only the most talented athletes are on all-star teams, and that the costs are obscene. Many school and rec cheerleaders don't understand that there are all-star teams for all ages/skill levels and that fund raising offsets the costs of tuition and other fees.
Get in touch with local school, rec and pee-wee programs and offer classes to help them stunt, jump, and tumble. If you work with the coaches of other programs to accommodate their schedules, many times they will promote your program to their kids and not view it as competition when recruiting.
Other ways to get seen is at local fairs and parades. Set up informational booths for your program and showcase some of your stunts and tumbling. That is a sure way to get some people interested in joining.
Get bumper stickers, and t-shirts. I can't go anywhere without people asking me how they can join my program. One staff member at my gym even had someone holler at him from their car in a drive though asking how they can join.
Well those are just a few ideas I had quickly brainstormed but the possibilities are nearly endless! I hope this helps you. If your have any questions feel free to ask.
Best of luck,
Coach Matt