That's fine.
We generally don't contract when it is a main verb denoting an action- I have lunch at 1pm (= I eat lunch), not [strike]I've lunch at 1pm[/strike].
Never, in AusE, and I suspect in most places. "I've" is only used for complex tenses, or in the irregular present tense verb, "I've got".Interesting... I agree that when referring to an action, contraction is rare. But when the action is distanced (so that it's not an action really, but a reference to the action) contraction is possible.
Example:
When can we meet?
Any time really, except...[looking at diary] .. except Monday, when I've lunch'
Or... not sure... perhaps you'd normally use a noun here - I've a lunch/a meeting/an appointment... :?:
b