For delivery, it seems like ebay already does all that and has a mature stable reputation, payment, and refund system.
"Kid stuff" just seems like another generic category alongside "outdoor gear" or "used elefteonics" or whatever that any of the big players already accommodate using their existing platform. Meanwhile you're trying to build a new platform that does pretty much the same thing, but with a much smaller network of sellers and buyers. Why should anyone use it?
Everything else is basically FB Marketplace, Offerup, nextdoor, craiglist.
If you can make an app that enough people use is questionable, let alone be profitable is another thing.
Whats the plan to make $?
Are there safeguards of any type for scams and the such?
I completely understand the difficulties in safeguards so this isn't a request, just a question.
Edit: might want to add Show HN to the title.