1. Don't know the answer to that, I suggest contacting the Singapore Consulate or a good travel agent that will help you with all documents needed.

2. Yes, you should be able to use your credit card (visa, mastercard...) in Singapore in most places (hotel, restaurants, "larger" stores. Just be certain to warn your bank that you will be traveling to Singapore so your card will not be locked.

3. Yes, Airports have money exchange counters. Depending on the airport (Canadian side), they might not have Singapore dollars; I'd check at a good exchange office if you can order some Singapore dollars.

5000 Singapore dollars is about 4700 Canadian dollars today; it is a large amount of money to have on yourself; I'd get a 300, 400 singapore dollars to get started and use local ATM machines to get some more if needed.

Question 1: immigration

As Canadians, you don't need a visa. Neither pre-arranged, nor on arrival. When you land in Singapore, you get in line at immigration, and get stamped in.

Visa on arrival is a procedure where you have to go to an office or counter, and apply for a visa, give a photo, pay for it, etc. That's not what you'll go through in Singapore.

Questions 2/3: money

Whatever you do, do no exchange money at the airport. They have the worst exchange rates. Withdraw money from ATMs, pay with your card. Many places (but definitely not all: one of my favorite restaurants is cash-only), including taxis, accept cards. My last trip there, I withdrew maybe 100 SG$, and used my card for the rest.

Your credit card will probably offer a better exchange rate anyway than exchange bureaus.