Give a child time to finish saying goodbye to something you are ready to replace.

Adults decide when an object has become junk, and by then they have usually made their peace with it privately, over some weeks nobody else saw. A child gets no such run-up. The attachment is not silliness. It is the practice of losing things, happening at a size they can still manage.

Say the replacement is coming before it arrives rather than after. Give them an evening with the old thing, let them keep one small part of it if they ask, and do not narrate why the new one is better.