Some suggestions for you off the top of my head:
Head i.Supershape 175cm - this has been a very popular ski over the last couple seasons, and with good reason. Some serious fun and energy in this one. Has all you can handle in edgehold. It's a narrow ski, but it has a nice wide tip, so it handles better than you might expect off piste and in the fresh stuff. It's worth pointing out that even in longer lengths, it's a very turny ski - it will do longer radius, but short quick turns are its favourite. That may or may not be an issue for you, depending on how you like to ski. At your size, definitely go for the 175cm, you'd likely be let down by anything shorter.
Rossignol Z9 - This is a popular one with instructors. It's a pretty versatile ski, but you definitely do give up some top end performance to get that versatility. It has a 74mm waist and 14m radius, so it's quite a bit less quick and turny than the Supershape. Decent edgehold, but won't perform wonders in real icy conditions, but given where you ski, that's likely not a huge issue. Comes in 170 and 176, again I would recommend the longer length for you.
Head Supershape Magnum - This is a new ski this season, but having tried it in the spring, I can tell you it's a winner, and a lot of people would agree with me I think. It's basically a stiffer and slightly wider version of the original Supershape above. Same great edgehold (I would argue even better), marginally less turny. The extra width definitely improves its abilities off piste. It's also quite a bit stiffer than both the other skis I've mentioned, which can be a problem for some, but at your size I wouldn't worry too much, unless you really don't want to have to work the ski much. Comes in 170 and 177, I would recommend the 177, but given the stiffness, the 170 could work as well, depending on your tastes. The big downside to this one is that it's a pricey ski, and since it's brand new you're not going to find any discounts on it until spring at the earliest.
For your granddaughter:
Head Sweet Fat Thang - This is a women's specific version of the Mojo 90, a fat twintip. It's very close to the Mojo, just comes in shorter lengths that would be more appropriate for her (and a different graphic, that she may or may not enjoy). Really good off piste ski, and since it's a twintip, she's got the option of trying some park skiing out (maybe not what you'd like her doing, but chances are she'd enjoy it). The downside is that it may be a bit wide compared to what she's used to.
Head Xenon 7.0 - this is a more conservative approach, quite a bit narrower and more of an all-mountain ski than one with an off-piste bent. Also new this year, but I've heard good things, a versatile, easy to handle but very capable ski. Would be a very good choice if she's still building her skills.
Rossignol Bandit B83W - Women's specific midfat that covers the ground between the Sweet Fat Thang and the Xenon. Forgiving, but has the width for plenty of off-piste action. Probably a good choice if she wants to spend some time improving her skills but keep a ski that will serve her well just cruising around her preferred terrain.
Those are just some selections, there are tons of great skis out there, so if you get a chance, the best opportunity is to demo and see what you like.
Some other ski lines to look at that I'm less knowledgeable about:
Atomic Nomad - heard some good things about these, also fairly new, there are likely skis in the line that would suit you and your granddaughter quite well.
Volkl Attiva line - Volkl's women line, there are some freeski oriented products in there, probably worth a look.
Fischer, specifically the RX Heat line would be worth a look for you. Sadly Fischer is almost non-existant in my region, so I don't get a chance to try them.
Edit: I just noticed you mentioning that you haven't had much shaped ski experience. I would highly recommend a lesson. A couple hours with an instructor would really give you a huge boost in making full use of your new skis.