What can I do to encourage children I mentor to be tolerant of other's differences if parents don't want an open discussion about it?

I believe strongly In encouraging children to be open and respectful of everyone regardless of their differences, That everyone should be loved regardless of their race, gender, sexuality, religion, or any other differences. With most of the children I visit/mentor/care for it’s easy to teach these lessons because I have the support of the parents in doing so.

However, for a few of the kids I visit I’m not as confident the parents would support direct discussions about these sort of things. In some cases I know the parents are not fully supportive of LGBT+ community or other religions, in other cases I don’t think the parents would say they are unsupportive, but I still suspect they would not appreciate my having a frank conversation with their child about these topics. For instance they may say the child is too young to discuss these things etc. I personally believe kids can handle honest conversations from a very young age and waiting to discuss important ideas is a bad idea; but it’s not my decision.

Given the nature of my volunteering it’s very important for me to respect the parents wishes, and so I don’t intend to actively discuss things with their children that I don’t believe their parents would approve of, regardless of my own beliefs. However, I feel there may be some smaller things I can do to help encourage children to be open to alternative views without saying or doing anything that the parents would actively disprove of my doing.

I’m looking for these sort of ‘subtler’ steps I can take to encourage children to stay open minded while being minor enough to not offend less open parents, or parents who believe children are too young to have frank discussions yet.

I visit children from early teens all the way down to toddler age, so I’m open for tips that would work with any age groups, Though most of my experience is with kids 7 and younger. I’d love to have ideas of how to encourage tolerance in any and all ages of children.