“We will have ... tomorrow” or “We have ... tomorrow”

The first one is correct.

Present tense: ‘we have a cricket tournament tomorrow.’ This has already been decided, and the speaker is reminding or informing his interlocutor of this plan, which IS already in place.
Future tense: ‘we will have a cricket tournament tomorrow.’ This is the statement that the speaker is deciding now to set up this plan, and the match WILL take place.

I agree with Brus and Hairy Scot.

Me too.

@Brus - And so do I, for once.
@Hairy Scot - I more or less agree with you, but as Brus says, 'will' suggests a decision at the moment of speaking (or at least that's how we teach it). For intention we usually use 'going to'.

There's also another possibility - to use present continuous, which we normally do to talk about future arrangements - We're having a cricket match tomorrow' - 'What are you doing at the weekend?'

In TEFL we teach four basic future forms:

'will' for decisions at the moment of speaking - I'll call you tomorrow
'going to' for intentions - I'm going to book my holiday tomorrow
present continuous for future arrangements - I'm meeting her for lunch tomorrow
present simple for scheduled events - Don't forget we have a meeting tomorrow.

They are both wrong.

@HJMCS - I'm afraid that's not good enough. With a moniker like that, we expect some highfalutin reasoning. (I think something's dangling there, but I really don't care)