Well if your sold on a 17hmr then you shouldn't have any trouble finding one. I taught my kids to shoot with a 22mag.
In any case a rimfire is a great 1st. choice I think. It helps youngsters learn about control, shooting dicipline, and it takes the fear out of report noise. And another thing...
My guess would be Roe deer.
Nice rifle in that picture btw. 100 gr looks like it penciled right through that fox! That's what happened to a coyote I shot with a 100 psp. He still went down like getting hit by a truck. I'm thinking a partition would have done much more damage.