I would suggest a Labrador retriever for the size and the friendliness, and they can get along with cats. (Read on how to get different pets acquainted with each other.) But there are a few caveats to consider. If you have a café, is food usually in reach for a dog? Labradors tend to have an insatiable appetite and they have some of the best noses among dogs. Since you have a cat, you've probably got experience with hair. How much of a problem would that be for you, considering that you have a café? Labradors are medium shedders. There are breeds that will lose much more fluff, but there are also breeds who shed much less. How much exercise do you plan outdoors? Labradors can be very well behaved in the house and are usually happy when they are around people. Like any dog they sleep through half of the day, but they aren't couch potatoes either. They love to be active in nature, they tend to love swimming and they are happy to sniff, search and retrieve stuff for you after a bit of basic training. They have a strong will to please.
You will find lots of information online about how to care for them. Just ask, if you have any questions afterwards.