>> I have a hobby of nature and iconic site photography-- please suggest me the places ... we will travel with our 5yrs kid in the last week of May for less than 10 days
May is a tricky time to travel in Switzerland if you want to see the alps. The ski season ends in most places in April, but the hiking season at higher altitudes does not start in general until the second half of June.
So April to mid-June is when many mountain transport operations close for 4-6 weeks for maintenance, which means you can't ascend the peaks for views. Other mountain transport operations close for the winter, and do not start reopening until between mid-May and mid-June.
Meadows at higher altitudes will have more of a brown or brownish-green look at that time of year, which is less attractive in photos than the vibrant green of summer and autumn. Summer in the alps is essentially July and August (but of course can vary depending on weather conditions in any particular year). September is also a lovely time of year for photography.
>> Is the Bernina express route is more scenic than other part of Switzerland?
It's very scenic, but there are countless other scenic routes and localities in Switzerland.
As you have 10 days and are travelling with a child, I would pick a maximum of 3 localities to stay in. Use the information on this website, a map, and the Swiss Timetable to help you decide what those localities should be.
Unless you want to spend the night in St Moritz to connect with the Glacier Express or Bernina Express, I would rule out spending time there, as practically all the mountain transport will be closed down. (The Glacier Express and Bernina Express will, however, be operating.)
Some regional trains travelling along the same route as the Bernina Express feature a photographers' viewing area. These trains are identified in the Swiss Timetable with the letters FW.
>> Scenic cruise --- which one is the best?
There's no single answer to that question. Of the lakes I have taken boat trips on, these are my personal preferences (in order):
- The Vierwaldstättersee (Lake Lucerne): dramatic mountains and traditional villages
- Lac Léman (Lake Geneva): vineyard terraces (less scenic in May, I would guess), traditional villages, mountains
- Lago di Lugano (Lake Lugano): Mediterranean feel, some interesting lakeside villages and at least one grotto restaurant.
- The Brienzersee (Lake Brienz): turquoise water and mountains
- Lago Maggiore (Lake Maggiore): the boat spends a lot of time far from shore, so in my opinion a boat trip on this lake is not so great for photography; this lake is also not covered by the Swiss Travel Pass.
- The Zürichsee (Lake Zürich): pleasant, but surrounding hills are comparatively low and heavily built up.
If you decide to go to Zermatt, these links might come in useful. Please note that some locations might not be easy to get to, or might not be accessible in May.