I hesitate, Tim. The place is located as far as 300 miles from my place, of which 2/3 lead through the most boring of Polish expressways (it is a freeway with the speed limit of 120 km/h while the regular freeway allows 140 km/h), and the remaining 1/3 is an exhausting mountain driving. When I was 37 (and my wife 30), we could drive up there on far worse roads with pleasure and thrill*. Nowadays, I'm getting tired of long driving.
The other matter is that region is very expensive now in August. It is because it is extremely attractive from touristic and recreational viewpoint. I would not dare to ride in the Karkonosze Mts, which are for "eagles". There is either bike ban or the hardest MTB trails there. It is doable to circumnavigate (to use that word) the Karkonosze around their base but that means multi-day credit-card tour. (A normal tourist uses their car, feet, and cable railways to explore Karkonosze).
On the other hand, the nearby Jizera Mts are easier to ride, especially via roads (my route is related to the Jizeras). Additional thrill is the fact more than half of the route is in the Czech Republic, and everybody likes to be abroad
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(I have to add the Czech have developed even better cycling culture and infrastructure than we Poles).
I think I will postpone the travel to the end of September when my gf returns to her London. I cannot take her to Jizera as she's never ridden e-bike yet and I'm sure she would not manage that trip. (Going to see Copenhagen instead and I swore to her we would be riding rented mech bikes there!)
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*) Polish roads were in terrible shape back in 1998. I was to go for a scientific conference to Karpacz/Szklarska Poręba at that time. Our first good car was almost brand new, and my (late now) wife Sheila had a brand new driving license
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We set off for the trip in the evening, and it was raining. I bit my teeth and drove all the way, trying to take the longer but better quality route. The next morning my wife transported the car back home. It was not a 300 but 375 mile driving, the first part through the most scary mountain roads! It was her first long driving! She was so proud of that!