You might want to check out this old thread from three years back: Riverside County GMRS 462.650mhz
In post number 5 I relate my info which pretty much jives with what you have.
Most recently, I haven't heard them very often - at least on those known frequencies they no longer seem as talkative as they once were. The most recent conversation I can recall of the SDINA group was on their Ultra channel, I think some months ago (that I heard). It seems like I only hear the WRRG group on the 462.650MHz frequency now and haven't heard SDINA in ages on that frequency.
Yes, you will hear the kids and such on those frequencies as they are part of the GMRS and, unfortunately, the bubble pack radios sold in department stores have GMRS channels as well as the FRS channels. Few people buying these things bother to read the fine print and obtain a license to use the GMRS channels (or just don't care anyway) so they use them on all of them, FRS and GMRS, however they like - kids playing around and all.
That's why the tones are very useful.