Minecraft purchasing options?

Looking for expert CAG advice on Minecraft for the PC.  My kids have Minecraft PE on our android tablets, but want to get the full version on PC.  I don't see it on steam or amazon, just on Mojang's website and I saw a download card at Walmart and Gamestop.  Are there any other options?  Are there ever sales or is it pretty much something you have to pay full price for?

Also, any tips for parents whose kids play Minecraft?

They had a Humble Bundle awhile back and it was available for 'Pay What You Want.'  I do not think they will go that route ever again.

At this time you have to go through them.

Years ago I got my kids to use Minetest. It's free. It's not EXACTLY like Minecraft but with mods it's pretty close. Most of their friends are playing Minetest and their schools use it also. The only time they play Minecraft is the free version that comes with Raspberry Pi but this is the PE version.

http://www.minetest.net/

I do not play minecraft but I do remember someone recently mentioning this in one of the pc threads. I think it might be the steam thread but anyway I searched minecraft and windows 10 and came up with this. I am not sue if it helps you or not as I know nothing about minecraft versions but it might be worth checking out. https://mojang.com/2015/07/announcing-minecraft-windows-10-edition-beta/ and http://blogs.windows.com/bloggingwindows/2015/07/04/announcing-minecraft-windows-10-edition-beta/ . Hope that helps some.

Like Cloulien said, I think the upcoming Windows 10 version may be your best bet for the full version.  Outside of the DL cards in store, I think Mojang is the only official place to get it.  One time GameDealDaily had it for like $15 I think but a ton of people got their keys revoked.  You might hope for a sale on video game cards in store and hope it qualifies.  I paid the $20ish for it a few years back and it was well worth it for me since I've put so many hours into it.  

My son plays it almost daily during the summer.  Well worth the money and it is not a mindless adventure unlike some other games.  My son loves discovering new things.   

Thanks for all the input!   Minetest sounds good, but my kids already have the original ingrained as they have several friends who play it.  My daughter's birthday was before the end of July when W10 comes out, so I just sucked it up and used a Gamestop GC I had to pay for $25 of it.  With limited options I figure they will get my money's worth out of it.  At least I'll also get the W10 version free later. 

just play trove on steam, it almost the same stuff, and it is free