You can order it from online suppliers, but I think they have to call it a supplement. It can be a PITA to order it, so I didn't mention it. You won't find it in your H&B or HFS. It's not as restricted in the US any more. Things like Truvia and PureVia are sweeteners with stevia as the main source of the sweetness. Truvia also uses a sugar alcohol. [EDIT: If you can get your hands on some Truvia, although it has a sugar alcohol in it, the one they use is
erythritol, which is the one that causes the least problems with gastro-intestinal side effects. It's also used with sweetening chocolate for people avoiding sugar, and is meant to complement the taste really well]
If you can get stevia, I'd still use some other sugar as well (unless you get something like Truvia). Some people find stevia has a really bad after taste, but that can be minimized a bit by using another sweetener or sugar. Some people don't detect it, but it could still ruin the taste of a cake for others.
If you are concerned about AS, stevia is still an AS and there has
been some concerns over the years about its safety. I think it is a safe bet to use with kids, not because it's natural, but because I think its ban has largely been political (but I also think some of the problems with some of the other--not all--AS has been political with the sugar and corn lobbies being behind the smear campaigns). It's probably a better bet than some of the sugar alcohols if you're avoiding GI side effects with little kids.