Hello! Your project has quite captured my imagination. I was thinking it might be interesting to contrast the forest to the the funfair with darker earth tones for the forest and bright, multicoloured lights for the fun fair.
I have a fair bit of experience animating horses, having animated one for my ongoing personal project, Kelpie, clips of which can be seen on the demo reel in my portfolio. The animation you'll see there is stylistically sketchy, but I am perfectly capably of doing clean lines in the Disney-like style you're looking for. I've also animated a fat pony, similar to the drawing you attached, in collaboration with a friend for a birthday present.
For a 7 second film I can have storyboards finished within the first day, done up in an animatic format (think moving slide show) and a few starter ideas for the design of the character.
Once the character has been finalized, and the animatic approved I can have a first pass of animation done within a day. It will likely take another two to three days for adjustments depending on your preferences and speed of communication (I can be available at any time of the day or night for reviews).
After that will be a day of clean-up and colouring. Two extra days may be added for animated fun fair elements if desired.
The remaining time will be used for adjustments.
I was wondering as to what personality your were looking for your horse to have. Were you looking for a slightly silly personality, a prancy personality, a proud personality, or a curious one perhaps? Did you want it to move in a cartoony manner such as Looney Toons' Pepe le Pew, or if you wanted it to move more like a real horse?
Also, will this project require sound?
Thank you very much for your time reviewing this, if you'd like to see more of my work my full portfolio can be viewed at Kendaroo.com.
Best Wishes,
Kendra Davey