THought I would post some info after my trip since I still had a lot of unanswered questions going to Donsol.
1. Whale sharks are AMAZING. The peak really starts in March though. We went early Feb, and were lucky to see 3 different whale sharks. The day before, we heard that some folks didn't see any at all. The problem is that b/c there are not that many, all the boats surround and share 1 whaleshark, despite what they say about 1 boat/1 whaleshark. The guides are great, and help those who are not great swimmers to get right up there and swim on top of the whaleshark. Even our 4 year old got to see them.
2. Some folks have asked whether it's possible to do this spending 1 day in Donsol. The answer is yes, if you are lucky to see the whaleshark that morning. You can fly in the day before, spend the night, do the whalesharks from 8-11:30 (when our boat headed back in), and then make it to the airport in time for a 2:45 flight back. We scheduled 2 nights, in case we did not see any the first day then we would try again the second day. Luckily, we did not need to do this.
The whale sharks swim fast, so I would recommend getting a personal boat, or having a second guide (extra 600 pesos) on the boat to help pull you to the whaleshark. Our guide was amazing, and he had us take turns 2 by 2 to take us out. He would somehow manage to position us exactly where the head would be coming, and then yell "look down" and there was the head of the whaleshark sure enough every time.
I would consider buying your own snorkels and bringing it there. They rent for 300pesos there, and are not very good. The entire town is monopolized (good for them to coordinate) so no use shopping around for different prices for things having to do with fireflies or whalesharks.
3. Even though we LOVED the experience, we did not want to do a second day. It is a little crazy with all the boats surroudning the 3 whalesharks in the water, so I dont know if I would spend the extra time in Donsol in order to do this twice. Plus, it is expensive.
4. I thought the firefly tour was lame. It is not like the river is completely lit up with fireflies, but that you would go to a tree, and one tree would be lit up with fireflies. and then you woudl go to another tree down the river and same thing. I would recommend it for people who have never seen a firefly before, but if you grew up with fireflies, I would consider skipping it.
5. We stayed at AGM, and outside our hotel was a long stretch of sand bar where we hung out and played on our second morning. It was a ton of fun and very relaxing. You can also see the whale shark boats driving around, and it was exciting to see how close you are just swimming to the whalesharks (based on the location of the boats).
6. You can do laundry by weight - our hotel charged us around 50Pesos/kilo which I thought was very reasonable.
7. You can go into town and walk around their market. It is very local and not touristy at all. You can buy fruit, or buy pastries and bread at this yummy bakery (on the outside of the square). We bought out these rolls that were like the portuguese sweet bread - each for 5pesos.
All in all, a great time!