Any suggestions for diabetic Christmas treats?

I was just going to mention Keto when I saw your mention of it. It’s one of the best things a diabetic can do. If you google Keto Christmas Treats, you’ll find a ton. Diabetics should do more than just give up sugar and Keto covers it all. Scores of people with diabetes have reversed it by going Keto. Some good Keto recipes are I Breathe I’m Hungry, Peace Love and Low Carb, Ketovangelist Kitchen and All Day I Dream About Food. Any treats from any of those sites are trustworthy.

One thing my mom has learned over the years is that she can handle simple sugars relatively well (most fresh fruits are ok, not juices and jams which are usually too concentrated), but she has very little tolerance for starch (cakes, breads, cookies-anything with lots of flour, rice, potatoes, cornmeal, oatmeal, etc). So I found anything that is flourless, or has very little flour works well. Though for some reason, she can eat things made from rye flour normally. With these basic rules of what works for her, it makes it pretty easy to bake for her!

I have made my mom these cookies, with a mix of bittersweet and semisweet chips, 1/2c sugar or maybe even less, and honey because that's what I had, and she said they didn't make her blood sugar spike: www.epicurious.com/recipes/food/views/chocolate-mint-cookies-102892
Flourless chocolate cake or friands, dark chocolate truffles, and dark chocolate peanut butter cups are all good. Just make sure whatever nut butter you use doesn't have added sugar. Amaretti cookies (again I try to reduce the added sugar) also work. Not good for shipping, but dark chocolate mousse is also something my mom can have. I think she's even able to have one or two macaron or meringues, even though they have lots of sugar, because they don't have starch (not good recipes to reduce sugar in though). Rye anything is great (I regularly mail my sourdough, 100% whole grain rye bread).

Nancy's suggestion of nuts and nut butters, infused oils, and chocolates all sound good. Artisan jerky or dry sausages would ship well too (more difficult to do homemade though, and again make sure there's not lots of added sugars). I would shy away from savory baked goods like crackers or breads because of the starch, or only include small amounts.

I'm going to end with a huge disclaimer. I don't know how common my mom's more permissive diabetes is (for lack of a better term? She works hard to maintain a diet and exercise regime that works for her) and I'm giving suggestions based only on my experience cooking and baking for my mom. I don't know how common it is a for a diabetic to be able to eat a macaron, but not a cracker. My grandpa also has diabetes that is much more severe, and things my mom eats with no problems are horrible for my grandpa. Talk to your parents and keep up to date as your dad learns what he can and can't have! And sorry for the book.

A few suggestions:
Nuts & nut butters
Savory (not sweet) baked goods. See this thread for some ideas (and there are many others around):
https://food52.com/hotline/33515-savory-bake-sale-inspiration

Less good for shipping (so, for giving in person), but good for adding flavor to his new diet:
Herbed and flavored olive oils
High quality fats (French or high fat butter, packaged schmaltz, artisanal lard, etc)
High quality dark chocolate