To goof around
To stand around
These are two I've never heard someone say or have used myself.
To fool around: I've seen it used by observers but never the actor. "Stop fooling around." It implies mischief, and not really the sort of laid back feeling you are going for.
To hang around: I have used "You want to hang out?" and "I am just hanging out." I have not used "hang around".
To chill: "You want to chill?" I have used that and have been asked it as well. Never asked or requested "You want to chill out?" That implies that someone is throwing a temper tantrum and needs to calm down.
So, the best one is 'hang around' but more like 'hang out'. 'To chill' could also be used, but without the 'out.' The others, I wouldn't used.
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