Since a few years I've settled upon Xubuntu, because I like the Ubuntu base and the XFCE desktop environment. Personally, I think it hits close to the happy mid

Since a few years I've settled upon Xubuntu, because I like the Ubuntu base and the XFCE desktop environment. Personally, I think it hits close to the happy middle ground between lean and minimalistic on the one hand and flashy with everything including the kitchen sink on the other hand. I think MATE (UbuntuMATE) is also virtually equivalent to XFCE (Xubuntu). Something like Xubuntu, UbuntuMATE, Linux Mint or elementaryOS might fit the bill for grandmas (and for me, as I want something that just works, is relatively simple and resource efficient and based on the traditional desktop paradigm).