USD will be best as the resorts there quote rates in $(food, room etc).

It has not at all been my experience that US Dollars are preferred in the Maldives, and I have been probably a dozen times. The public ferry will take US Dollars for the fare to cross from the airport to Male (US$1) as will taxis on Male, but my guess is that you will not be taking any local ferry trips or taxis (and using US Dollars means you will slightly overpay verus paying in local currency). Baros will collect you at the airport and take you by boat to the resort (charged to your hotel room.) Places like the airport cafe will take US Dollars or other curency to buy a cup of coffee, but that is the case in most any international airport.

Your hotel most likely charges in US Dollars, but you won't want to carry around that much cash and would use a credit card.

In any event, you won't be using much cash at all in the Maldives, as everything you do will be at or from your resort where you will have one bill, paid by credit card. Your hotel bill will cover all food and incidentals like water sports which may not be included in the room price. All your meals will be at your resort, unless you go to a nearby resort for a meal, in which case you can also use a credit card or local currency (they may take US Dollars for a meal, but I would use a credit card to get a better rate). Even a day trip to a nearby "inhabited" islands (which some resorts offer as a chance to see local life) will be put onto your hotel bill. There is little to buy on those trips, as you are looking at local village life. You can pay for anything you might buy in Rufiyaa.

While Baros is quite close to Male, with only 5 days I would not spend any of it in Male. It simply offers too little to see to justify taking a half day from your hotel. If you nonethelss decide to go there, you can get cash at ATMS, there are several (including a Citbank and an HSBC) along Boduthakurufaanu Magu, the main street which fronts the water. If you take a taxi in Male, you will entirely miss the point of Male, which is about 1 mile square and entirely walkable. (Taxis are for people with luggage going to hotels on Male).

I suppose you could tip hotel staff in US Dollars or Sterling, but as they will just have to exchange it for Rufiyaa, I would tip in Rufiyaa.

If you want local cash, there is an ATM at the airport, just after you collect luggage and head out a set of doors toward the arrival hall, look left. There is also an foreign exchange counter there where you can exchanage money.

Back from Maldives mid sep we changed one hundred dollars currency at the airport, and had a heck of a time getting rid of it, you only need usd

Yep USD is the most widely accepted currency for a typical tourist(those that have been there less than a dozen times) to use for tips and buying gifts etc.

If we go into Male to eat dinner, do they accept U.S. cash?

We have a late night flight (11:30 pm), and I guess the sea plane will put us in Male around 5:30, so that's 6 hours to find something to do...