As for your question about bringing a lot of "basic" stuff for children, Kurt, parents like having this stuff (e.g., porta-crib, high-chair, stroller, etc.) so that the parents can relax as well. We travelled with our children since the first one was 3 months old. At a minimum, we always had a stroller. We'd order cribs from hotels (we didn't stay in vacation rental homes when the kids were young -- frankly, didn't know about them and wish we had!). And the kids would eat on our laps if there weren't high chairs. So, perhaps that's why I'm sensitive to kids and parents -- I can think back to what we wish we had. And I know how great it feels when you find that someone has thought of these things for you, and it's good to pass that feeling along.
As for people ruining vacation rentals, we rent mostly to families and smaller groups. We have not had problems (other than what we would consider normal wear and tear), except that once I left a small suitcase labeled "Owner's clothes -- please leave on shelf" and it was gone the next time I came back a few months later. Could have been a guest or a substitute cleaning person, but once in over 3 years is OK with me -- and, of course, I didn't leave my best clothes in the bag. (and I don't leave bags of clothes around anymore).
I'm biased toward renting to families with children because they are so happy to find a nice place that is close to the beach and has the stuff they need to give their kids a good time so they can relax. I believe that in return for that appreciation, they treat our places very well, in part because they want to come back again. Also, I think families with children, especially young children, try to set a good example for their children. Note that it's also good to leave nice stuff for the parents --good movies, books, candles, etc., so they feel treated well, too. And Calvin and Hobbes for teenagers and older children...
Once summer, we had an origami book and paper at one of the cottages and people left their origami flowers in a vase -- very nice. We like to leave things in the cottages that draw parents and children together so that both parents and kids remember their vacation as having been relaxing time spent together (e.g., books in which parents and kids can search for things together -- "I Spy"; puzzles; games). A fantastic family game is "Outburst" for kids -- kids as young as four can enjoy the game along with older kids and adults (e.g. "name foods that you can eat with your fingers"; "name pets that kids enjoy most").
Clearly, I'm a believer that the environment significantly shapes a person's behavior, experience, and emotions (at home, at work, on vacation), so that's why I'm so interested in this thread. How do we create carefree vacation places that bring out the best in people and provide lifelong memories? Clearly, our beautiful beaches (even after hurricanes) and ocean help!