You can drive but it depends on weather. If the Sun is high, I would love to suggest you guys a car... The roads are awesome...
Athirapalli waterfall doesnt allow you to shower you exactly beneath it... but you can enjoy playing in water at the top before the falls...
wayanad's soochipara fall allows you to get wet with its water...
for soochipara, visit my profile and read an article about it.