My puppies have done very, very well on Wellness Puppy kibble with a small spoonful of wet mixed in to make it interesting. They are fat, happy, and very active. I have tried a lot of different dog food over the years with my dogs, but this is the one that they ALL love the most.
I, personally, think 7 weeks is way too young for a Yorkie puppy to leave its mom and siblings. But, since it has been decided, I would just make sure he is safe and happy. They will eat anything (and then choke) so don't take your eyes off of him unless he is safely in his crate. Also, don't over play with him. Naptime is very important when they are so young. Since he is only 7 weeks, make sure you socialize him. I think it's important that you do that - but only after he has been given his puppy shots of course. Good luck on your new puppy. Would love to see pics.