I have a brother whose child was, um, very emotional as a baby/toddler/preschooler. Tantrums (and just not the "norm" tantrums) and I was really bothered by this. Everything they did made it worse (there were other dynamics effecting it, too, since my SIL has RA and my brother tried to "protect" her and not having her parent, but she abdicated the parenting on her own a lot with out any assistance from my brother). I had the nerve to suggest maybe counseling (my brother, this toddler's dad, was in counseling as a child for his terrible temper....) or a parenting class so they would have more tools in their toolbox to deal with the child's out of control behavior..... BIG MISTAKE. It took a long time for them (particularly SIL) to forgive me for that.
In another case, with a particular prickly family member who often takes offense when none is meant and who holds grudges, it was clear that the sleeping patterns were physically effecting their youngest child's life and growth (no, I'm not kidding). The mom is a cardiac nurse, and worked the night shift, and would allow the then-6 yo to stay up until 2 or 3 in the morning on her nights off so they could "spend time together" even when the kid had to go to school. Lack of sleep actually affects growth, and his poor sleeping habits continue (slightly less bad now); he is the shortest kid in his class by _a_lot_. Anyway, I tried the subtle approach by approaching my brother (instead of SIL) with an article from the New York Times that talked about sleep & its lack & how it effects kids (among other things, human growth hormone is released during certain parts of sleep, so if you don't sleep enough as a child, you will not grow to your full genetic potential). My brother thanked me for the article, but utterly failed to grasp that his child was the unnamed reason. I should've been more point-blank, but frankly I will have to deal with this SIL for the rest of my/her life and I didn't want the feud.
I felt very slightly better for having tried, but mostly awful because a) it didn't change, and b) I still worry for the kids (fortunately, the toddler in the first instance has finally matured a bit and has better emotional control... at age 10....).
The hotdog thing, I probably would've said point blank, "You should be cutting up the babies hotdogs. They are a major choking hazzard." For the other (climbing/falling), I probably would've said with a smile, "I don't think Abby has any clue or ability to understand the results of her curiosity. She doesn't understand that she could fall and get seriously hurt; 2yos just don't get that kind of cause & effect. Have you thought about [putting up baby gates; not letting her climb on chairs; etc.] or redirecting her to some other activity?" Of course, I say this thinking, "Yes, but what if the mom is one of those that overreacts/gets angry/holds a grudge? What would I say then???"