With kids and luggage, I’d do the route via Zurich that doesn’t require bus connections. If you’re coming from Como you don’t even need to go to Milan at all. You can take the Gotthard-Basistunnel from Como to Zurich, skipping Milan and the construction altogether. If you leave at the right time, this option only requires 4 changes Como > Zurich > Interlaken Ost > Lauterbrunnen > Grutschalp > Murren — the direct trains from Zurich to Interlaken Ost only go every 2 hours, so if you time it correctly, it’s going to greatly simplify this day. For example, if you left Como at 7:54 on July 5th, you’d arrive in Murren by 1:54 pm or leave 9:50, arrive at 3:54. I’d personally do the early one to get settled into Murren and still have some time for exploring before dinner.
To know what pass to advise, you have to list out every activity you plan to do, price it out on SBB (pricing defaults to half fare card) and compare. It takes a while. I’m pretty fast at it, but there is no getting around doing all the calculations. I’m happy to help but can only do so once you put together a pretty specific itinerary.
For the kids, there is a Sportzentrum in Murren. When you pay your tourist tax you get a pass to enjoy their facilities (indoor pool, hot tub, virtual reality room, outdoor soccer field, skate/scooter/bike ramps, etc.)
Obviously weather dependent/flexible, but I’d recommend something like this….
*Saturday - arrive in Murren by 2 pm, drop off your luggage (right across from the train station), explore the village, optional walk down to Gimmelwald or Sportzentrum
*Sunday - Schilthorn + Birg Thrill Walk in the AM, Allmendhubel funicular for lunch, playground, hiking in the afternoon (Northface Trail counterclockwise or Blumental Flower Trail)
*Monday - Murren > Grutschalp > Lauterbrunnen > Wengen > Mannlichen (kids would probably enjoy the extra 5chf riding on the top in the open air part of the cable car) > optional Royal Walk, alpine playground > easy walk to Kleine Scheidegg > optional detour to Falbodensee (Kniepp baths) > optional hike or train to Wengernalp > train to Wengen for exploration > Lauterbrunnen (more exploration) > Grutschalp > Murren
*Tuesday - Maybe Schynige Platte open air cog train up to viewpoints/hiking/lunch OR time walking down to Gimmelwald and exploring the farms + walking through the Lauterbrunnen Valley seeing the waterfalls OR if you want to brave the crazy crowds, Grindelwald First (not my “first” choice, ha!)
*Wednesday - Murren > Luzern - explore old town
*Thursday - boat ride to Vitznau + Mt Rigi?
*Friday - Luzern > Zurich Flughafen