I also don't use the g word. I don't think it's an accurate concept anyways, plus, everyone should be able to have an optimal learning environment, whether his/her IQ is 99, 101, 129, 131, 144 or 146... I definitely share with parents who are interested about enrichment resources, ways to talk with teachers, organizations, experts, etc. I have never proactively approached someone though, if they feel things are fine, I wouldn't tell them otherwise. :-) For me, this kind of conversation usually starts when a parent complains that a kid is bored at school, or he/she can do so much more but what school offers is so limiting, etc.
On the receiving ends, sometimes people would tell us things that we have tried long ago. That's why I feel awkward because I don't want to appear less grateful than I should be; but I also don't want to say "yes, we tried that and it didn't work" too many times...
