Venice to Lauterbrunnen area to Paris

I think Rome2rio.com and seat61.com will help you explore your transit options. If you take the train from Paris to Southampton, you'll need to change to a train leaving from a different station in London. As long as there are no delays you'll be fine, but if there are any delays you could miss your boat if you don't get at least to somewhere in the U.K. the night before.

For Switzerland, it looks like there might be some options to reduce your costs: http://www.ricksteves.com/travel-tips/transportation/trains/switzerland-rail-passes I don't think a multi-country pass will help you since Eurostar or any flights you take wouldn't be included.

Hotel Jungfrau in Mürren was my favorite place to stay. It's high up on a cliff and very peaceful up there. You can hike right from the hotel that way. Wengen would be similar, but it has cars I think, whereas Mürren is essentially car free.

The Eurostar train from Paris to London takes around 2.5 hours, and you have to be there at least 30 minutes ahead.

The train arrives at London St. Pancras station, and your train to Southampton will depart from Waterloo. To connect by Tube, you will have to make one change between lines, so allow around 30 minutes for that.

The train from Waterloo to Southampton takes 1.25 to 1.5 hours. It is a pleasant trip---we did that last week.

If you add it all up, and allow extra time to find your right track or tube line, plus connect time mandated by the train schedule, it comes to a minimum of 5-5.5 hours---assuming everything goes smoothly. I would not want to out on that and would leave Paris a day ahead and overnight in London.

I neglected to mention the lodging part. We have stayed in both Wengen and Mürren and like both, but there are more hikes from Mürren. A place there that would suit your family well is the apartment at Chalet Fontana. It has two bedrooms, one with a double bed and small single bed ( for parents and youngest child) and one with two twin beds ( for the two older kids). We stayed there with our family a few years ago and it was fine---and we enjoyed the opportunity to cook meals as the restaurants in Switzerland are very expensive.

I neglected to mention the lodging part. We have stayed in both Wengen and Mürren and like both, but there are more hikes from Mürren. A place there that would suit your family well is the apartment at Chalet Fontana. It has two bedrooms, one with a double bed and small single bed ( for parents and youngest child) and one with two twin beds ( for the two older kids). We stayed there with our family a few years ago and it was fine---and we enjoyed the opportunity to cook meals as the restaurants in Switzerland are very expensive.

dk,

Transportation between the places you'll be visiting is actually quite straight forward. A few thoughts.....

• Venice to Lauterbrunnen - there are numerous trains on that route, but it's going to be a long travel day. I'd probably use a departure at 07:50, arriving Interlaken Ost at 14:28 (time 6H:38M, two changes at Milan and Spiez, reservations compulsory on first two segments). There will be an additional transfer at Interlaken Ost, as you'll need to take the short 20 minute ride from there to Lauterbrunnen.
• Where to stay in Switzerland - As you want "to discover the entire area", I'd suggest staying in Lauterbrunnen as it's the transportation hub and the most convenient location for getting to both sides of the valley. Staying in Lauterbrunnen will minimize transportation times while staying there and also when you leave for your next stop, and also minimize transportation costs while touring in that area.
• Lauterbrunnen to Paris - One of the easiest trips will be a departure from Interlaken at 08:30, arriving Paris Gare de Lyon at 13:37 (time 5H:07M, one change in Basel, reservations compulsory on second segment). From Gare de Lyon, you can use Metro or Taxi to reach the area of your hotel.
• Paris to Southampton - it's a bit risky to travel on the day your cruise departs, but if everything works according to plan, it's certainly possible. I'd probably use a departure from Gare du Nord at 07:13, arriving Southampton Central at 10:49 (time 4H:36M, 1 change, reservations compulsory on second segment). That's going to be a long day as you'll have to check-in at Gare du Nord at least 30 minutes prior to your train, or you won't be riding. Also, you'll need to allow time to clear Passport control for England.
• Passes - I'd have to spend some time doing some number crunching, but the only Pass that comes to mind for the places you'll be visiting is a Half Fare Card for Switzerland. For the few trips you'll be taking on trains with reservations, it's usually cheaper to buy advance tickets, especially in Italy. However with those, you must travel on the trains you've booked, as the tickets are specific to train, date and departure time. If you board the wrong train by mistake, you'll be subject to hefty fines which will be collected on the spot! If you use any Regionale trains, Buses or Metro in Italy and don't validate tickets prior to boarding on the day of travel, there are also hefty fines. The same is true of the Vaporetti in Venice.

Good luck with your planning!

I too like to stay in Lauterbrunnen. Muerren is lovely, but Lauterbrunnen gives you easier access to both sides of the valley as well as to Interlaken and the lakes. We stayed in this apartment just last week. 2 bedrooms, less-than-10-minute walk to the station and shops.

You'd have to do the math on a pass, but a Swiss Half-fare card plus the Berner-Oberland Regional Pass were a winning combo for us to make the costs of lifts and trains less of a drain on the budget. The Half-fare card gave us 50% off each train trip in Switzerland and a significant discount on the B-O pass.

that's a pretty amazing trip, hope it doesn't kill you.

One thought for Lauterbrunnen to Paris is to take the Golden Pass from Interlaken to Montreux, change to Lausanne, TGV to Paris. If you want more scenery.