I think the trouble I have at keeping everyone at arms length when it comes to our kid's issues is that many of our relatives have relevant experience. We have people who were accelerated, people who went to gifted magnets, gifted people who went to plain old public schools and even other 2e's.
We have all that in our families too. I think part of the difference may be in family personality - my dh's family (which has dyslexic family members and I'm guessing other older relatives with expressive language challenges) just doesn't tend to talk about this type of thing. So on the one hand, that's good, because it means no one is offering up not-asked-for-advice... but otoh... it also means our ds had been already diagnosed for several years before we accidentally found out he has a cousin with exactly the same challenges... and honestly, it would have been helpful to know that way before he was diagnosed

The trouble is that since they (or their kids) turned out just fine they think what they did or didn't do is the way to go. Actually everyone turned out better than fine.
It's not always easy to see this when you're in the midst of struggling with possible 2e issues (or any kind of a challenge).. but, fwiw, parents of typically developing non-gifted non-athletic not-much-of-anything-out-of-the-normal kids can also act this way too. Sometimes it helps me to not personalize comments like this as related to the actual issues my child has or to my parenting, but to remember the comments are coming from the personality-type of the person who is making the comments. That at least makes it easier for me to brush the comments off and ignore them.
I get comments like
"Who cares if he is dyslexic. It isn't like he'll be illiterate. He'll figure it all out without any greedy therapists involved in his little five year old life. He'll figure out what works for him and be fine. He is an engineering type. There are worse things than being an engineer you know...(cough)...lawyer...(cough)"
And
"I am pretty sure the gifted program at my school was cancelled to provide new carpet for the football locker room. I turned out fine. Just pick a house you like. It isn't like you are trying to choose between the school district where they might be maimed and the one where they might become drug addicts."
Honestly, I might tell you the very same things with the absolutely best of intentions and because I care. My child is older. He is ok. In spite of that not being delivered in the ideal way as a message, there is caring behind it and there can be understanding - I (and perhaps your relatives) have once been in the very place you are now worrying about your child and not knowing what is going on. Try to just tell yourself they care and then change the conversation to something that's easier to talk about.
And I know - totally easier said than done!
Hang in there -
polarbear