If its the one in pernera, about a 15 mins walk from protaras they only have a couple or so rides and its expensive for what is there. Its a place where mostly youngsters go whilst parents are sun bathing, and can keep their kids amused in a safe environment.
Water world near Ayia Napa is set in beautiful surroundings and has a lot to offer your children at that age, they will not want to leave.
Taxis will give you a voucher for a couple of quid off if paying at the gate, my advice is go to the local Thisvi shops dotted around protaras, Pernera and Napa, they give you the actual voucher to go straight in with, so your in the shorter line to get in. it is cheaper than the gate price and reps prices at the welcome meeting.
Please do not take any food in, they do random bag searches, including back packs.
If going on the bus it costs 70c pp, we always get a cab back, remembering to barter first
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If you go in a cab both ways, the cab wont charge you until the return journey.
I hope that helps.
Michelle.