Is this just adolescence?

Okay. This may just be adolescence, but it's starting to drive me nuts. Mr. Knightly gets a walk first thing in the morning and again in the evening. About an hour total.
Right now I'm working from home, but I'm no longer freelancing, so I don't have as much flexibility with when we go for a walk etc... during the day.
He's just at the point right now he won't entertain himself. This morning I tried to let him just stay up with me (rather than putting him in his kennel) and he just sat their and whined. So I put him to bed. But the afternoons are when it gets challenging.
After he's napped and usually around 2PM he loses all interest in entertaining himself. His stuffed and frozen Kong keeps him busy for about 30/40 min. After that he whines, fusses and is basically a pill. He simply won't entertain himself or chew on his toys.
I'm going to be ordering the buster cube and I've ordered some more pressed rawhide (we're out).  I want to be patient and know he wants some attention. But he's got to get better at entertaining himself. I also don't want a spoiled puppy who always has to be the center of attention.
There's a little guilt in there that I can't give him all my undivided attention, but at the same time he does get a lot. We would do more during lunch, but he usually pretty sleepy still and doesn't want to really play.
Like I said we walk twice a day and we spend time playing together in the evenings. Not to mention both my parents spend time interacting with him in the mornings and evenings too.
Are my expectations unrealistic? What should I do when he sits their and whines (and we've been to the bathroom etc...)?