The most stereotypical belief about clients is that they are made only for billing amounts!
We all have fun at the workplace, in the meeting, around dining table… (actually, you can say everywhere you can think of). Having fun in the workplace is vivid, this fun is the fun of having a job, it's a good thing, it's comforting in a way! I call it "The fun of work".
Trust me, work can indeed and honestly feel something very much like fun. When you are working well, when you are engaged, involved, challenged and interested. What you do becomes what you love to do, something that makes you forget the crazy you do when you are bored or stressed and find yourself completely into the job at your hand. This may not be just a 'Ha-ha' kind, but it is fun the genuine fun, deep real fun.
The fun of work is being a part of a really good meeting where everyone is participative and 'Listen' to one another, everyone has something to contribute. Having fun at the workplace makes you feel together, individually and collectively. You listen to each other more closely, to yourselves more closely. You build the team.
The most fun places to work is the place where the fun is upheld, shared and supported. Anyone can have fun, but the company to be fun itself, the top level has to not recognize fun but has to have fun. Recognize what fun means to your company, your employees and the work. There is a kind of freedom in the fun, the freedom that gives you opportunities to learn from each other, to find like-minds, and to connect, build a relationship.
Remember, informality is always better than the formality. A buffet is more fun than a banquet. A bunch of learning centers is more fun than a lecture. Give them things to do together. Lots of things. Different things. Think kindergarten.