I have been in both the coasts and the tea garden area. What is that you want to look for? Urban comforts means Colombo, decent beaches are along both the coasts, but I prefer the east coast for personal reasons.
Colombo - Didnt spend a lot of time here, went to Galle roamed around for a day, stayed the night there and left to Kandy by car. Visited the elephant orphanage on the way, kids loved it.
Kandy and Nuwara Eliya is like our Darjeeling, Munnar area - Hilly with plantations. Stayed near the Lake (booked through airbnb), a nice old colonia house. Lake, Buddha's tooth relic and the botanical garden are worth visiting. There are lots of plantations, so you can stay here for days just doing nothing. There is a sightseeing train that runs between Colombo and the tea country, but you have to book them in advance.Dambulla caves and Sigiriya rock is another thing thats a to-do if visiting this area, it's a bit of a longish drive from Kandy, but I was anyway going to east coast, so it was on the way for me. I didnt stay the night there, moved on to Trinco.
East coast - My fave area - I visited Trinco and the beaches around that area. Stayed in the Anilana Nilaveli resort north of Trinco, Piegeon island is a small boat ride away where you get see sharks, corals and turtles. I also visited the Thirukoneswaram temple, its steeped in Tamil and hindu history. The original temple was destroyed by the Portuguese, but a new temple has been built there. The port area is nice and modern with decent coffee shops, places to sit and a pier that you can walk to.
I didnt get to go to North or South East, there are some good wild life parks in the South east. Like any tropical island, weather is a bummer and when it rains it pours. Roads are not express way types, and in some places it would look like India pre 90's, broken single roads. English is spoken and understood and ofcourse Tamil works in the tamil areas. Public transport is very in-adequate, mostly traveled by cabs/tempo traveler types. Inside the city, we can take autos. The food is something that you relish, if you eat seafood, a combination of Tamil/Kerala cuisine. Its not too expensive to visit, if you book a little ahead, the tickets are cheaper than going to MAA-DEL.