A sentence beginning with "What if" introduces a sense of hypothesis, assumption, or condition, which doesn't reflect the current reality.

This construction follows the rule of conditional clause, in which the verb is in the simple past.

Other examples:

What if it rained? Would you still go ahead with your plan?
What if you won a lottery? Would you still keep your job?

In your situation, you could also ask: "How about meeting tomorrow?" or "Could we meet tomorrow?"

A sentence beginning with "What if" introduces a sense of hypothesis, assumption, or condition, which doesn't reflect the current reality.

This construction follows the rule of conditional clause, in which the verb is in the simple past.

Other examples:

What if it rained? Would you still go ahead with your plan?
What if you won a lottery? Would you still keep your job?

In your situation, you could also ask: "How about meeting tomorrow?" or "Could we meet tomorrow?"

NOTE: The answer addresses OP's concern that what he said could be incorrect, which is not. "What if we meet..." isn't wrong either. It may be a suggestion or invitation.