There is nothing wrong with the Maldives. 99% of tourists just go off to a resort and never interact with local people. Incredibly boring, but hey, you can name drop Maldives later.

I would go with your NZ+Fiji/Tonga plan.
That way you won't be bored on a beach for 2 weeks.
And it won't break the budget.
However, I would skip NZ in July.