I think I need to be more open, so DS understands what we have, what it took to get here and gratitude for where luck played a part. And so that he knows what it will take for the lifestyle he may want to have in the future.
This is important to DH and I too - that our kids understand how privileged we are, and that the lifestyle we enjoy in our mid 40s is not what they will have starting out - if at all, depending on what line of work they chose, amidst other factors. So we try and be quite open about money, and never say "we can't afford it" but instead explain in terms of "if we spend money on X we couldn't have y" (even if it was "if we bought a Ferrari we wouldn't have a house to live in"!)
DS innocently repeated the common saying "spending your inheritance" that he heard his grandmother say about one of their upcoming trips. My ILs are quite wealthy and travel a lot. That led to a dinner table conversation about how they had worked hard for their money, have the ability and application to learn how to manage and grow it, the good fortune to be able to do that, and that it is their money and we shouldn't expect anything. Instead it's about being grateful when they use their money to take us on holidays, buy presents etc.