Right now, OpenSports does not have an age or position filter. You can use the event invite filters to filter gender, availability, sport, and level. We will be adding a position filter soon.
Once you have created an event, at the top of the invites screen are tabs that allow you to select which category of people you want to invite from: Your Group; OpenSports Users; and Phone Contacts. Within those categories, you can use all of the filters.