This has been really helpful, thank you!
A little background on our babies: Odin and Dos share a dad, actually, but obviously from different litters. Daddy is a big 200 pound boy. Dos' mom was around 160 and Odin's mom was less but comparable (though the exact number escapes me at the moment).
Yes, one is still a puppy and our one year old (Dos) is still in many ways puppy-like, but she has, surprisingly, taken on a more mature role now that we have the younger pup (10 weeks). Not that she doesn't charge on and play, but she seems to be more concerned with making sure she knows where the little one is and if playing together will obviously focus all of her attention on him (Odin). Now, this very well may be my own perception shift since I didn't have the comparison before! We also spoke to our vet and she reminded us that it doesn't behoove the breed to play too rough with puppies so as to ensure the continuation of the breed. Makes sense. Also makes sense to keep an eye on things just in case.
In any case, I think I was nervous because, while Odin is a big puppy (26 pounds) , he still remains smaller than Dos. Seeing her put her big mouth around Odin's much smaller limbs or body was a bit scary but she also hasn't bit - only stops him. I definitely want them to learn to play well together (and let the pup learn good behavior appropriately) so will try to relax a little bit and let nature take its course. I think the advice to also remove the puppy if necessary was really useful because I needed reminding that our big girl can't be entirely responsible. At night, when it is bed-time Dos lies down near Odin's crate and they kiss each other, so I know they like each other but once out together it is NON STOP!