we have a similar wooden trike Wild Things from ELC DS has played with it every single day for the last two years, he loves wizzing round on it! He now pushes DS3 on it too which is cute but scary as he's only 14m!
We got DD a large one for her 1st birthday and she loves it. She's 20 mths now but has been sitting/riding on it since about 15 mths and she's probably more on the petite size. IMO, they'll outgrow the small one very quickly.