Gloves protect your hands, not your head.
It is actually safer to use lighter gloves, from the perspective of brain trauma. Research suggests greater brain trauma is suffered from boxers (8-14oz gloves) than MMA fighters (4oz gloves) because boxers take a high volume of shots, versus an MMA fighter that would have been knocked down or out, and finished from the same strikes with a smaller glove. It sounds crazy, but you would actually receive the least brain trauma wearing no gloves! You would get more cuts, and more wrist injuries, but punches that should finish the fight would actually finish the fight.
For the sake of your fight with your friends, I would suggest using the smallest gloves you can find, just to help with cuts so you don't look like a psycho at work on Monday. Don't be tough guys about it. If someone gets rocked, stop the fight.
Don't use headgear. The science against it is overwhelming. Headgear causes unnecessary torque from what should have been glancing blows, which causes concussions, and neck/spinal damage. The only thing it really helps with is cuts from headbutts.
Don't use wraps. All wraps do is protect your wrists, which allows you to punch harder, and with reckless abandon. You would rather have sprained wrists than damaged brains. Wraps are nice for hitting the heavy bag, but when your friend is on the other end of those punches you want want to be able to hit him with an artificially stiff wrist.
Here's a source, but there are tons more if you'd like to do your own research.