JEM provides a lot of different modules to present events but none of them is designed to mix events with articles.
The main reason is the different view: on articles creation date is a good indicator, but on events that's less or not important. Instead visitor want to know when event starts (or which events start on a specific date). And because creation date is always in past but event start date in future (otherwise visitors become depressive) I don't see an intuitive way to mix articles and events.
Instead you can create two modules - one for latest articles, the other for next events. You can show them as clearly separated modules which own title each or try to combine them on same position with one title only (but of course having articles and events in one group each).