idea of the picnic / idea for the picnic

[sb70012]

Hello,

Idea = plan/thought
[countable] a plan, thought or suggestion, especially about what to do in a particular situation.
1. It would be a good idea to call before we leave.
idea (of something/of doing something)
2. I like the idea of living on a boat.
idea (for something)
3. He already had an idea for his next novel.

Source: http://www.oxfordlearnersdictionaries.com/definition/english/idea

I'm bewildered about the usage of [for] and [of] in this self made example:

Alex, what's your idea ...... the picnic we have tomorrow?

(I want to say Alex what's your plan for tomorrow picnic.)

Which preposition is appropriate in my self-made context? of the picnic or for the picnic?
In my opinion, both are ok. But what's your opinion?

Thank you

 

[Biffo]

Alex what's your plan for tomorrow's picnic?

 

[sb70012]

Alex what's your plan for tomorrow's picnic?

Thank you but I wish you could gave me some more explanation that why can not use [idea].
If it does not mean plan?

Thank you

 

[PaulQ]

Alex, what's your idea for the picnic we have tomorrow? - What's your plan for tomorrow's picnic.

Alex, what's your idea of the picnic we have tomorrow? -> What is your opinion of tomorrow's picnic.

Although I agree with Biffo - plan is better. Idea can mean plan or proposal or opinion.

 

[sb70012]

How tricky and difficult to detect the difference.
Anyway, thank you Paul.