If I only have 10 people will my event have a good atmosphere?

It's a tough one. It very much depends on the event and what you are going for. If you want a low-key event then a small number of guests is perfect. If, however, you are going for a big lavish event then 10 people won't be enough.

On the whole though, I would say that the number of guests is irrelevant to the 'interest value' of your event.

People won't be thinking about how interesting your event was because there was loads of people there. Instead, they'll remember how interesting it was because of everything surrounding the event.

Providing you plan for the number of people attending then your event will run perfectly. It's then a case of keeping people's interest. That can simply be done by providing quality entertainment. It doesn't matter what the entertainment is, as long as it fits with the style of event.

If you are planning a low-key event then aerial acrobats are probably not the right kind of entertainment. It doesn't work with the style of the event and, while interesting, isn't particularly relevant to the event.

The entertainment is the interesting stuff, that's what people will go away talking about, not the number of people in the room. In fact, no one is bothered by the number of people in the room, especially when they are entertained and given something else to think about. 

That's the key. Don't worry about your guest numbers, make sure they have adequate entertainment and your event will be remembered for many years to come.

All the best,