This is the part I pretty strongly disagree with you. There is a reason "Comparison is the thief of joy" is a popular saying. People are pretty quickly going to be exposed to the reality of the situation, at which point the gap between their fantasy and reality will be a huge demotivator.
In any case, there are lots of free stock image sites you can use to find images that actually depict reality. Not saying they aren't staged, but there are lots that I think would be "friendlier" to newbies, which is what your site is about.
New to me! But it’s great and I will use it. A related one that I use (with my kids) is “Don’t compare your insides to other people’s outsides.”
I think it looks fine, and ads some visual cues for what the activity actually is.
https://www.pexels.com/search/bouldering/
https://www.pexels.com/search/grandmother%20and%20grandchild...
The reason, though, that I think it's especially bad for your project is because the whole purpose of your site is to try something new. I like the saying "Be brave enough to be bad at something new". So many of us get into a vein (often subconsciously) of always comparing ourselves to others because basically all of the examples we see online are the 0.001% experts that make it to the top of some feed algorithm. So, for example, why use a "perfect model specimen", complete with fake veins, for your "Bouldering" example, https://www.whataaabout.com/imgs/bouldering.png? Why use a "Hallmark card perfection" example of a (fake) smiling grandmother and her daughter, https://www.whataaabout.com/imgs/familyTree.png, for "Creating a family tree"? An almost fairytale scene for "Scavenger Hunt", https://www.whataaabout.com/imgs/scavengerHunt.png (though apparently some of the cars in the lower right are about to be sucked into another dimension).
Your site should be about people embracing the joy of the reality of doing something new, not more fantasy land bullshit that doesn't exist.
Sorry, will get off my soapbox now and go back to eating my soup.