It's a pretty ambitious project, and the flowchart of robot operation is one of the easier tasks, or at least it's one of the later tasks.
First you need to get the 2 servo wheel motors hooked up and coded, then interface the sharp IR distance sensors and get them coded.
Then start on the basic blocks of the operation, like code that uses the sharp sensors to tell a moving object from a non moving object, which is not that easy if the robot is to be moving at the time!
Then if you want it to map the environment and know where it is, that is a huge leap again in difficulty and processing power, and it's not really necessary in order get the bot functioning as planned (to follow a cat).
My suggestion is to start closer to the beginning, then tackle the higher level brain functions after its lower level brain functions are workign and defined.