while Im fully in favour of boosting numbers for OUFC matches, with what happened at yesterdays abandoned FA cup 4th preliminary round match in mind, bringing friends and family along should be absolutely fine, beyond that erring on the side of caution may be an idea, as OUFC supporters may not know the character or likely behaviour (at live football match) of friends of friends of friends or very vague acquaintances.
Boosting numbers so every home game is sold out would be great for the clubs finances and many other benefits too, but applying a bit of caution regarding who is invited may also be prudent too