Just to check I'm reading this correctly - 4 of you are travelling, 1 of you has status and none of you has access through ticket class?

As you can only guest one person into the lounge, that leaves two who don't easily have access. You cannot pay for lounge access at T5, so your options would seem to be - find two people with status who are willing to guest in one person each (the method has already been suggested), buy upgrades for two people to ensure access through ticket class or hope that the desk agent would bend the rules for you and allow two extra people in with you (which would be risking the humiliation you wished to avoid).