While a Mini is a chiropractor's meal ticket, it's relatively easy for grown-ups to get in and out of the 500's rear.
Once ensconced, there's enough legroom and headroom
for two six-footers to sit comfortably in the back, even if the tiny rear windows limit the view out.
Boot space in the 500 is also fairly reasonable. It holds 185 litres with the rear seats in place, so you should be able to jam in a quartet of soft sports bags.
Flipping the rear seat backs towards the front of the car boosts the luggage space to 500 litres. That's easily enough to haul a tent and enough cases of lager to get you through a summer festival weekend.