Grindelwald, Lauterbrunnen or Interlaken

Congrats on the wedding!
Have you considered Murren or Wengen- that would be my choice- BE in the Alps, not looking up at them. When is the trip, as Murren currently has some noisy construction in progress?
Safe travels to this beautiful country!

If you enjoy "non-touristy" spots, I think I would avoid Grindelwald. Perhaps visit for part of the day, but not 4 nights. I really liked Lauterbrunnen. I thought it was very central. No 5 star hotel, however. I agree with the above poster that Murren and Wengen are lovely, but again, I'm not sure about a 5 star hotel.

Would highly recommend the Hotel Bellevue in Wengen/best view of the Lauterbrunnen Valley and very nice breakfast room and restaurant and you can also eat on amazing terrace with view… get a room facing south.

I’m with you Micheal. Those views from the hotel terrace the best we have experienced. Maybe not a five star…but lovely and romantic! Food and their breakfast very good. We loved Wengen!

In April you are looking at highs of 46 degrees. Snows is melting, etc. A lot of restaurants and hotels may be closed until the summer season, especially in the smaller towns. All of that said, I really love Wengen. Lauterbrunnen may be more lively at this time of year though. And by lively I mean that you may be able to find more than one place for dinner.

I would want to wake up each day, open the balcony doors, and see the view of the mountains directly across from us. That is, Id rather be in the mountains (Mürren, Wengen) than at the foot of the mountains (Interlaken) or in the valley looking up at the mountains (Lauterbrunnen). Nothing non-touristy about any of them, but nature overcomes the human presence, in the quiet Swiss way.

Note April might still be ski season, with snow on the ground, and trails closed, so not the flower-blooming warm meadows that might come to mind.

First of all, congratulations!

In those circumstances, these are the three choices I'd consider.....

1. Lauterbrunnen - it's the transportation hub for the area, so if you're planning to do sightseeing on both sides of the valley, it would be a good choice. Although not "up" the mountains, the views are beautiful enough for me, and I'm usually out touring in the daytime anyway. I usually stay there as it's so convenient.

2. Mürren - this is a beautiful alpine village, and is higher up the mountains so offers spectacular views. Depending on which hotel you choose, you may be able to enjoy those views from your hotel balcony. It's a good choice if you're planning to visit the famous Schilthorn, which was used in the James Bond movie, On Her Majesty's Secret Service. Mürren is only a few minutes from Lauterbrunnen.

3. Wengen - it's on the opposite side of the valley from Mürren and also offers spectacular views. The hotels seem to be a bit more "upscale" in Wengen. This is a good home base if you're planning to visit the famous Jungfraujoch, which is short ride up the hill from Wengen (change of trains in Kleine Scheidegg).

Grindelwald or Interlaken would not be my choice.

Another vote for Wengen. Lauterbrunnen and Grindelwald will be much busier, since they are accessible by cars. I wouldn’t consider Interlaken if budget allows for a 5* hotel. Be in the alps, not half an hour away.

The views from Wengen are stunning, and there are several fancy hotels to choose from. Wengen also makes it easy to to go up and over the mountain to Grindelwald via gondola. The Eiger Express is a great trip. Should be lots of snow still in April. Many of the trails had just opened when we were there in June.

April isn’t really ideal for visiting the mountains as the weather is transitioning and some hiking/cables/trains/restaurants may be closed, but what about finding a beautiful hotel on Lake Brienz or Lake Thun and then traveling up into the mountains for a couple day trips? There are some really beautiful hotels on the north sides of both lakes that are away from the crowds with Mountain views and near boat stops. I’ve also heard good things about the 5 star Park Hotel Vitznau on Lake Luzern.

Have you considered the top notch Dorint hotel at Beatenberg? Great views, great service. Great location, esp. for April. Have a look at https://hotel-interlaken.dorint.com/en/

I second the poster who suggested Luzern! We were there in November so our weather was likely similar to what you will experience in April. At that time of year there shouldn't be many tourists even though Luzern is a major Swiss tourist attraction.
From Luzern you can take mountain excursions to Pilatus, Rigi, etc. assuming there are no semi-annual maintenance closures.
https://www.luzern.com/en/. There are spa resorts nearby that would be a romantic honeymoon setting, e.g. https://burgenstockresort.com/en

Hotel Staubbach in Lauterbrunnen. Request/book a room on an upper floor with a balcony and view of the falls. You will be centrally located to nearly all points. Much construction going on near the cable car station in Mürren. In April there will not be many others than locals there. The cable car from Lauterbrunnen to Grütschalp will probably be closed as well as from Wengen to Männlichen.

Note that star ratings for hotels in nearly all of Europe have more to do with amenities rather than how swank the hotel may be. You need to do your research if you are going for "posh". Staubbach is not posh by any definition but has a spectacular view. Hotel Silberhorn in Lauterbrunnen is more upscale and closer to posh but lacks the views you would have elsewhere. I cannot recommend any other hotel in Lauterbrunnen.

I agree with the recommendations to stay up in the mountains, even with the seasonal issues. I stayed in Murren, and completely splurged on a chalet from vrbo (it was a special trip), in low season. The construction did not bother us, but it may be over then anyway. I would check Wengen as well given what others have said about the hotel availability, but definitely check rentals.
These places being popular did not bother me since I was out on the trails all day.
When you say 5*, share your budget per night, as you may get some specific recs that way.
congrats!