Puppy more interested in other dog, help!

We have an older dog, he's around 9 years but we're not sure as we got him from a shelter, and he's a really laid back dog when it's just family at home, although he does bark like crazy at strangers. Helio is absolutely in love with him, he looks up to him for everything and wants to play with him all day long. The problem is though, Dobby (our older dog) obviously doesn't have the energy that Helio does and Helio doesn't seem to know when playtime is over. Dobby will jump up on the couch to get away from him and Helio will just bark and bark, trying to jump up (he can't quite get on the couch just yet) and bite his face so he'll come down and play with him instead of sleeping. When he does that, I'll stop what I'm doing and give all my attention to Helio, and we'll play together so he doesn't feel like he's missing a playmate or anything, but after about 10 - 15 minutes, he gets bored and runs away to bug Dobby again. He seems to like Dobby's attention more than any of ours, and I don't want to stress Dobby out or anything, so what can I do to get Helio to want to play with us more?

It's also frustrating because in all the things I've read about training, including the book by Dr. Dunbar, it says to get the dog to stop biting, you should yelp and leave the dog alone, so it knows, "Hey, playtime ended. I need to stop biting so I can keep playing!" But when I do that, Helio reacts in a way that I always take as, "Oh well, I don't really care about playing with you anyway. Where's Dobby?" Also, Dobby has tremendous self-control, so he doesn't really bite at Helio and Helio's bites don't bother him to the point of ending play, other than when he jumps on the couch, and that doesn't seem to deter Helio. Can anyone help with this? It's just very frustrating.

First, this is pretty typical. And second, I've got a similar situation in my house at the moment (puppy and 2 year old dog). Guinness jumps on the couch to get away from Thistle if he doesn't want to be with her (he has stockpiled all his favorite toys there too).
It's important that your older dog is able to escape from the puppy if he doesn't want to play.
I think playing with Helios may be rewarding him for annoying Dobby. You should separate these 2 actions, maybe move into a different room before starting to play? It only needs to be a minute or so of "between time".

Even better would be to work on Helios' training while Dobby takes a break. There's nothing your older dog would like better than a well behaved puppy.
You could also encourage some quieter play time (Using a kong or bully stick to get him to settle down). I feel that often puppies go crazy when they are getting sleepy, imagine a toddler running around screaming "I'm not tired! I'm not tired! aaaaaaah!" So if you slow him down in his craziest moments (training, chew toys, petting him while singing to him) he may just doze right off.

You do need to make sure Dobby has a safe place to go. If Dobby is comfortable in a crate you might offer him that option to escape the puppy, be sure to shut the door so he doesn't get ambushed in there. Otherwise baby gates, if Helios is a particularly good chewer be sure to get one with wire lattice (there are some designed for dogs, most of the "baby" ones are plastic).

It should settle down over time. At first my puppy would not leave my cat alone. My cat actually plays with my dog so its really cute Then it started getting annoying, seems like they would just go and go and never stop. 4 months later and now they can walk by each other without having to start a wrestling or chasing match. Once the initial excitement is over and a routine is established things should calm down quite a bit. For now when things get out of hand just make sure your older dog has a safe place to go and redirect your puppy to a different fun activity!

Hang in there!