The ropes you need to descend canyons of Crete are 60-65 meters long. Those ropes cover 99% percent of rappels in Crete canyons. For canyons like Arvi (Rmax 82m), Lapathos (Rmax 80m) or similar with high waterfalls there are middle points that you need to reach and change ropes. If you can not, then bring a 90m rope. One in a team (group) is enough.
The neoprene suite you need for canyoning in Crete in Spring time is 5mm to 5.5mm.
Water temperature in Crete in April is 12-16 Celsius degrees.