Bernese Oberland in May

Most rail links will be open, since some of them are required for local residents. The Jungrfraujochbahn operates year round. Just checking the Maennlichenbahn cable car in Wengen, it opens June 1, so I think the first week of June everything (or 90% of everything) will be running. The cable gondola on the other side from Grindelwald opens May 19. This year, the Schilthornbahn from Muerren to Piz Gloria was scheduled to shut down for just a few days in late April and 30 days from early November to early December for maintenance.

As far as weather, who knows? You could show up June 1 in the rain and everyone will tell you "You should have been here last week. The weather was beautiful!" Even in June, depending on the weather the previous winter, there could still be snow left on some of the trails.

We visited the BO in mid-June and found out that a couple of important hiking trails were going to open 4-5 days later. If possible, I would visit the area as late as possible in June. Regarding the weather and rainy days, it is unpredictable regardless of when you visit.

I went in July. The problem with May is that the higher the altitude you go the wetter it may be from the snow till melting from the winter. By July you could still see pockets of snow on the ground near the Schilthorn Mountain

As I understand, the general consensus is May is better avoidable.Mid-late June is probably the earliest time to visit these places (not considering the winter season)

I will try to postpone my trip but may not be possible. Also, July-Aug is difficult for me to take holidays because of work commitments. What is the alternative time? Is early Oct a good time to visit? What is the start and end time for the peak tourist season? I was hoping to avoid the peak tourist season if possible

Late May is NOT too early to visit the BO. I've visited several times in late May and the wildflowers are in full bloom. Trains, funiculars, gondolas up and running, restaurants and hotels open for business. Murren is my home away from home.

I think the first week of June would be fine. Mid October, you can run into snow.

I will be in Murren myself from 22 - 26 May and then one night in Lucerne. I follow an individual that lives in Murren Twitter account and this past May during the last week it was sunshine and flowers in bloom. In 2017 there was snow on the ground on 23 May, but all melted away and sunshine by 26 May. Lets hope for good weather, all I know is I will be there and not here.

I've had lovely times in mid to late May all over the Lauterbrunnen Valley - both sides - and up into the mountains. If one lift is out of commission use the others or the trains. By late June the crowds are too thick for me.

I was there in mid-June and the Allmendhubel funicular was closed for maintenance on the Murren side (a lot of hikes start by going up the funicular and grandually winding back down). On the Wengen side the Mannlichen-Klein Scheidegg hike was closed until June 15th I believe due to snow/mud conditions.

Mid- to late-May is a great time to visit the B.O. Spring flowers, smaller crowds, great weather, and lots of lodging options are why it's my favorite time to visit. High elevation trails will probably still be closed and some special lines may be down for maintenance, but there is no shortage of things to see and do. You might even get see it snow briefly!

Thanks, everyone.
I am still not sure as it looks like there are some conflicting views.
I will try to push my itinerary to early-mid June.

Any suggestions on the place to stay? I am thinking Wengen or Grindlewald?
I heard Grindlewald may be crowded but considering this is not the peak tourist season, I was thinking it might be fine and there might be more activities in the town to keep family busy.