I don’t blame you in the least for being worried about a name that you may feel will give the child problems or ‘label’ him or her. I’d be upset/worried, too.
I know it’s popular to pretend that certain names don’t have connotations with a capital C, but the fact is that some names do, perhaps especially over-twee double barrelled, or made up names, or those with a ‘younique’ spelling that’s going to mean the child having to spell it out for ever more.
Unfortunately it’s probably unwise to say anything, unless you want to cause a rift.
Mind you, I’ve heard of prospective parents mischievously telling their own parents/in-laws that they’ve chosen some particularly way-out name - just to see them valiantly try to hide their horror - before confessing that it’s something much more mainstream.
You never know, maybe your relative will ask on the baby names thread on Mumsnet, and have 95% of answers saying Please Don’t Do It!!