Agree that the drives are long. The roads are 2 lanes - one in each direction with lots of old trucks and giant buses that have a lower speed limit than cars which means it can take a long time to get from place to place. And you'd be driving through the mountains as well. So I think that is unrealistic to drive that far in one day including a stop in Kandy - which deserves at least a day on it's own.

I traveled with Kulansa tours which is a very small operation. But there are many other tour operators that offer the same sort of service with a driver/guide to take you around the island.

I liked Ella a lot. The view from my hotel out over the valley was spectacular. The hotel itself was fairly basic though.

I visited Yala and didn't find it especially crowded. We arrived before dawn and had to wait for the gates to open. It was a little bit of a free for all at first but then people spread out a little bit. Saw a few leopards which was apparently somewhat rare and caused a stir with lots of jeeps racing to the same spot - they communicate with each other by radio.

For just 1 week I think your plan might be a bit too ambitious. Perhaps limit yourselves to the cultural triangle area plus Kandy and tea country. There is Minneriya National park with tons of wild(-ish) elephants and lots of tourists close to Sigiriya. So maybe get your fill of animals there.

I spent 2.5 weeks doing Colombo, cultural triangle, Kandy, Nuwara Ellya, Ella, then Yala, an overnight at the Boulder Garden hotel followed by a morning at the nearby national park which I will have to look the name of, Galle and then a couple of quiet days on my own Ngombo. It really is a gorgeous country.