A good place to go if you like a sandy beach and an arcade full of pre 2000 and post 2000 barcrest etc etc is dymchurch 3 arcades although the fun fair arcade only has about 20 machines or so they changed the rest to ticket machines with crap prizes like most big arcades nowadays be warned though some have more bulbs out than are working.
Can't speak for the over 18 area though I was banned from that area when the 500 s16 games were introduced and I dropped £500 the first day the machine went in so they banned me from that area.
IMO that was the worst thing they ever did as I always started with a few quid on the £5 jackpots and worked my way up to the bigger jackpots now once I get to £50-£60 quid I leave and stick 2 fingers up knowing I would have lost it years ago on the bigger jackpots.