2 Days in Lake District (including a cruise). How to maximize the intake of beauty/experience

There are plenty of drives that one can take within the area all of which will offer fantastic views, there really are no 'bad' views in the Lake District so no need to worry about missing out on a specific area. Just be mindful that driving can be a challenge due to the narrow roads, livestock etc so if you have no experience of countryside driving in the UK I suggest watching some YouTube videos to help prepare your expectations. As for rainfall, you're travelling in August which should be the driest month but that means very little as far as the UK is concerned, particularly the Lake District, however you are unlikely to experience days of steady, heavy rainfall.

Unfortunately I've only ever passed through the area, never stayed so I cannot offer any advice on hotels.

Two full days (two nights) in frankly not enough to enjoy the Lake District.

If you are taking the train from London, you would likely take the train from Euston to Windermere via Oxenholme. Lodging options are an easy walk from the Windermere trainstation. You can ride the Windermere ferry across the lake and get a shuttle (or walk) to the bunny lady's farm.
https://www.visitcumbria.com/amb/bowness-ferry/
https://www.lakedistrict.gov.uk/visiting/localspecialities/famouswriters/beatrixpotter
https://www.golakes.co.uk/Sawrey-Hill-Top-Beatrix-Potter's-House/details/?dms=3&venue=5014450

If you are coming from Windermere or Bowness you can cruise or catch
the Ferry across the Lake then the seasonal bus link (from the
beginning of April through to the end of October) between Ferry House
and Hill Top.

By Boat: The Windermere ferry between Bowness and Ferry House offers a
low-cost, frequent and scenic link to Hill Top for visitors based in
the Bowness and Windermere area. The footpath from Ferry House to Hill
Top is comprehensively signed. The Cross Lakes Experience provides a
package via Windermere Lake Cruises from Bowness to Hill Top using
boat and bus.

Other lake cruises:
https://www.visitcumbria.com/lake-cruises-boat-trips-lake-district/

Launches operate lake cruises and boat trips in the Lake District on
Windermere, Derwentwater, Coniston Water and Ullswater. Windermere is
the only lake with a car ferry.

Unfortunately, two days does not give you much time to do any serious fell walks.
https://www.walkingenglishman.com/lakeswindermere.html

Windermere is forever identified with the romance of the Lake
District. The lake is the most well known of all the districts lakes
and it draws in visitors all year round. In Windermere and
neighbouring Bowness there are plenty of activities to keep visitors
occupied even in times of inclement weather but perhaps less known are
the wonderful range of walks which can be accessed locally. It was
near Windermere that Alfred Wainwright, the famous fellwalker and
writer of the Pictorial Guides to the Lake District discovered the
Lake District when he viewed Lake Windermere from Orrest Head. It is
simply and wonderful place with wonderful walks in the surrounding
district, some of which can be found on this page.

You could walk from Windermere to Grasmere and take the bus back if you are a Wordsworth fan, or just enjoy the scenery and village if you are not a fan.
https://www.visitcumbria.com/amb/dove-cottage-wordsworth-museum/
https://www.visitcumbria.com/amb/grasmere/

Bus service:
http://www.lakedistrictonboard.com/bus-attractions.html

Re Rain. Prepare for the worst (rain. wind and hail) and hope for the best.

Our last visit to the Lake District was a late May walking holiday starting and ending in Windermere with overnights in Grasmere and Coniston. Warm blue sky walking days to Grasmere then Coniston. Forecast for the walk from Coniston back to Windermere was favorable with just a chance of showers in the afternoon. Afternoon chance of showers turned out to be several hours of thunderstorms and rain so heavy we must have walked by the signs to Hilltop farm. At some point we were walking in calf deep water (on the road). By the time we got to the ferry, rain stopped and by the time we crossed the lake, sky was blue. Three hours of rain in three days.

I spend lots of time in the Lakes and usually base myself in Keswick. With children it's a good town for you...lots of places to walk, a beautiful park down by the lake where they can run around, and a family atmosphere with lots of kids and dogs! If you want to rent a car you'll want to take a train to Penrith, not Windermere...there are no rental agencies there. From Penrith it's a 25 minute drive or so to Keswick. Derwentwater, the lake that Keswick sits on, have beautiful wooden launches you can take around the lake. They stop off at several docks around the edge...you can get off, walk around and let the kids play, and then get back on again and continue around the lake. I wouldn't worry too much about rain in August...I've been there when it's been extremely hot and other years it is cool with intermittent rain. You just can't tell in that part of England - the weather is very changeable. Chances are it won't be a concern though. From Keswick it's an easy drive to things your kids might enjoy like the Castlerigg Stone Circle, a lakeside walk at Buttermere, just walking down a lane and looking at beautiful Herdwick sheep, or arranging for a farm tour. Beatrix Potter's home, Hilltop, is about a 30 minute drive from Keswick over in Sawrey. There is a ton to do there but just know that in August the area is very crowded with tourists.

With two small kids, try to include Beatrix Potters Hilltop house. There are illustrations from her books throughout the house and the children will love seeing where the stories of Peter Rabbit and the other wonderful animals were set.

Another vote for Hilltop with the kiddoes - if they know Peter Rabbit. The vegetable garden and house look just like you would imagine. It has been left as it was left.

Pretty good for the adults, too.

Beatrix Potter's Hill Top Farm
https://www.youtube.com/watch?v=KToF5YMhmEc

One of the most visited places in England's Lake District National
Park is Hill Top Farm. It was owned by Beatrix Potter, the creator of
Peter Rabbit and nearly two dozen other children's classics.

And then there is the "attraction": The World Of Beatrix Potter (That I haven't visited).
https://www.visitcumbria.com/amb/world-of-beatrix-potter/