Oh girls thank you so so so much!!!!

I hope you don't mind if I pick your brains over the next few months while I plan. We want to pack in as much as we can (going away for 3 weeks) so I would really appreciate it if I can have as much info as possible!!

We were originally going to travel up north to Chiang Rai and Chiang Mai and the Golden Triangle but we have decided that we want to spend more time in the islands so we have changed our minds on this. Unless someone can tell me why I should absolutely go there???

So the plan is this:

Phuket (2 days)
Koh Phi Phi (5 days)
Krabi (3 days)
Phang Nga (Overnight)
Koh Similan (3 days) - this is a 2 night/3 day snorkelling and camping tour
Koh Samui (5 days)
Koh Phangan (3 days)
Koh Tao (2 days)
Bangkok (3 days)

This is really only a rough plan. I would appreciate feedback on the following:

Is April a good time to travel? i.e. weather
Is there anywhere that I am not staying long enough, or that I am staying too long at?
Am I travelling to these places in the right order?
We want to avoid the bulk of the crowds so where are the best places to stay in each place?
What are your best recommendations for activities?
What is a "must do" activity?
What should we give a miss?

That's all I can think of at the moment!! I'll be back with more as I think of them! Thanks so much girls!!!!