I've not had elderberries or currants but i've been raised around gooseberries and have some at my place now. I like them but i wouldn't recommend them for smoothies. Gooseberries are a touch seedy for smoothies. Also, with gooseberries early in the season when they're green they're sour. This is when i like them best. Raw as a snack, halved and tossed in a fruit salad for a kick, or i've turned them into jam. The upside for JAM is there is no need for pectin. The green berries have enough naturally occuring pectin. My wife enjoys them later in the season when they start to turn a purple color. They lose their tartness and gain a very nice sweetness. At this time they'd probably be ok for a smoothy. The bigger issue is if you let them get purple the birds will be on them in no time unless you net them.
Other things (good or bad) that i've noticed.
1) They spread. Birds eat them no matter what you do and then poop them out somewhere else. I have them in one spot initially. 3 of my neighbor's have them now in their fence and i've spotted them under several trees in the neighborhood now. Seed grown ones aren't always 100% faithful to what you plant, but they're pretty close.
2) Easy to propagate.
3) Good brush for nesting animals or small animals looking to get out of the sun. My cats love it in the summer. Bunnies love them as well.
4) Thorns. They have them...doesn't really mater the variety. Easy enough to avoid them but they are there.
5) Good fence row. You can grow them along a fence and or treat them like a fence row. If they're in full sun they can get to about 6-7ft tall for older canes. They can get dense enough to keep most things out except small animals that will go under them against the ground.
6) They do need pruned from time to time. Especially if you find dead/unproductive canes or canes that have mold on the them. Not hard to do in the fall/winter (that's when i prune mine).
7) I've peeled them and used them similar to willow trees to make a rooting water with some degree of success. Not as good as willow but still passable if you have nothing else.
Hopefully someone can provide you the same thing for the others that i have provided here for the gooseberries, but i lack the specifics for them.