Need advice for a 6-7 days trip to Srilanka in Mid October

Hello all!
We are planning for a 6-7 days trip to Sri lanka in Mid October (roughly 15-21) We are a family of four, we like to take things easy (not rushed), love nature and beaches (bit of activities if there are must do). Places we have in mind currently are Sigiriya, Kandy and Bentota ( 2 days at each locations). Do you have any better suggestions? Most welcome. Also suggest best travel hacks, tips on food, cabs, etc. Between Kandy and Ella which would you suggest and why?
Thanks in advance for your suggestions.