lauterbrunnen / interlaken in may

Many of the activities you've listed are specific to the summer (except snowboarding), and the summer season in the mountains doesn't start until June. The Berner Oberland does not have year-round skiing (like Zermatt), and I think the pistes have closed for the season by now. You can probably do some hiking, but the high elevation trails will not likely be accessible yet.

" it gets smelly due to fertilizers?" If you visit coincides with the period when the farmers spread the manure, yes, the air can smell a bit ripe.

Isn't it great to have Chris on this forum! Maybe I'll run into you June this year in Murren...

It's true that they spray the pastures in April with liquid manure. It's also true that many hotels close for "shoulder season" which is a transition period from ski season to summer season. However, not everybody closes. Check with your hotel to see if they are open. Many should be in early May. We've been in Muerren in late May and it was just beautiful. No snow and the weather was warm. The wildflowers were in full bloom. We did not detect any of the manure smells. No guarantees on the weather however.

thanks so much for the tips!

just need some more help in deciding where to stay...

1. is it better to stay in lucerne, interlaken or lauterbrunnen?
2. does anyone know how long is the travel time between these places?
3. which is a better trip/experience: mt pilatus, mt titlis or jungfraujoch?

thank you!

"which is a better trip/experience: mt pilatus, mt titlis or jungfraujoch?"

The answer in May depends on the weather. Whichever gives you a clear sky when you're in the vicinity.

That's a lot of things you want to do in 3 or 4 days in Interlaken region :)

Do note, that unless you own/rent a car, travelling time is also subject to train schedules, gondolas/cable cars timings etc.

Some places are closed and only open late May/early June - as I've just found out (I'm writing now from Wengen). So if you were planning hikes in Shynige Platte or Mannlichen (please pardon my spelling) - please make sure the cable cars etc that take you there are open.

I would recommend Grindelwald First as a nice location to go to. You could go up in the cable car, all the way to the top where there's a nice view (subject to weather). Thereafter, you could take the flyer (sliding in a seat on a steel cable over 800m) down. From the next station, you could pick up a scooter (trotti??) bike and zip all the way down. The view along the way is nice during spring time. I believe you'd be looking at Eiger's north face as you ride down.

Jungfraujoch has gotten very touristy. I'd go early as the tourists seem to pour in from late morning till all afternoon. It gets very crowded.

Don't bother staying in Interlaken.

You can do paragliding at Lauterbrunnen, near Stechelberg (at the far end of Lauterbrunnen). They jump off Murren. So you could kill two birds with one stone there.

Check out the Via Ferrata that goes from Murren to Gimmelwald.
https://www.youtube.com/watch?v=BQnE3HCVERg
Check out that video to get a better idea!