We need beautifully designed winner/achievement certificates for kids

Information for the business: We sell rocking horses
Design details: We need several A4 award certificates that would appeal to 6-10 year olds, boys and girls. We would sell/give these with our rocking horses. A parent could fill in the child's name. Obviously a horse-y theme. Interested in choosing a few differing styles, and paying per certificate.
We would need you to pass copyright over to us to use and edit as we want - please note in your reply that you accept this condition, and please do not reply if you do not.
Output should be a PDF and an .ai/.png file. Colour fine.
Plan is to choose 3-6 certificates and to pay £40 per chosen design.
Target audience: Kids 6-10
Ideas for the visual style: Horses, Cowboys, Show Jumping, X-country
Extra notes:
I would suggest drafting a design for you reply. The more complete you draft design is the easier it will be to choose you.