Going to Tonga in October - Advice please!

Hi, my brother and I are going to Tonga mid October from NZ for a brief 5 day trip (cheap flights courtesy of AIRNZ!)
We're a bit torn as to what to do with our five days without trying to cram too much in - by the sounds Tonga isn't a place where rushing is encouraged!
I originally thought we could fly up to Vava'u and spend 3 days there then come back to Tongatapu, as I'm really keen to get some whale swimming/diving in. However it is quite a decent amount to fork out for flights, so was thinking we could spend out time exploring the islands off Tongatapu and maybe spend a couple of days on Eua.
I hear there is whale watching off Eua too? Can someone please fill me in about this. Does it rival the 'whale experience' of Vava'u? Are you able to swim with the whales if you happen to see any?
What are the offshore islands like? Namely Pangiamotu, Fafá and 'Atata? Are they within kayaking distance of Tongatapu? If not how do you get to them?

I hope someone can help me out here! :)

Fafa is a basically just a hotel. Hotel guests are ferried on a hotel owned boat.

A strong kajaker should be able to reach it from the pier in NukuAlofa, but then again, the island is so small that there is nothing much so see and I did not find the restaurant to be worth while at the time I was there.
A good point: There is a beach and you can use it on Sundays - and every other day of the week, of course!

Great, thanks for the advice. My roughly planned itinerary is as follows; arrive late Thursday evening, stay at Toni's. Fri do Toni's tour of the island. Saturday head out to Pangaimotu for some snorkelling/relaxing, Sunday go to a church service and wander around (i assume there are no markets on sundays?), Monday morning fly to Eua, do some hiking, Tuesday whale watch/dive the cathedral then fly back to Tongatapu at 4.30pm. Is this going to be risky as we fly out of Nuku'alofa for Auckland Tuesday evening at 9.30pm? Just HOW unreliable are the flights Eua>Tongatapu??

Flights on Chatam seem to be pretty reliable these days but I still wouldn't leave things so tight.
Bad weather, for example, could mess things up.
It would make sense to start with Eua.

I know nothing about the new airline operating, but it used to be very unreliable because of the weather. I've been a few times to Eua and only used the plane once because it was so bad. Trouble is, I can't remember what kept grounding the plane - they almost always went to Vava'u and Ha'apai OK.

I can't believe Toni is still around! He's alot of fun (provided you aren't offended easily).

Toni is definitely around though several of us found him a bitter, grumpy old bag of bones now and fled his place (now poorly located 3 kms from the city center) for better options after a night or two.
But his place is still cheap and in the new house (he offers accommodation in 2 now) even very nice, and his round-island tour still popular.

Right I've swapped everything around so that we're going to Eua on Friday morning returning saturday afternoon. Also realised that it would be v. foolish to dive on Tuesday and then fly out to Auckland on the same day!! From what I've read in reviews Toni sounds like an interesting character..... We're fairly thick-skinned so we should be fine haha but we'll see! How long does it take to get over to Ha'atafu by bus from Nuku'alofa?