I personally have never kept a puppy strictly indoors until after all vaccines. Never even heard of such a thing until joining YT. That is prime socialization time, and I would've gone crazy... are you allowing the pup into your own backyard at least?
I think skipping dog parks and pet stores is a GREAT idea (def. too many germs) but yeah, don't be terrified to take your pup outside. Just be aware of any possible parvo outbreaks in your area. My vet was totally fine with Jackson going outside after his 2nd set of shots. I brought him home at 9 weeks and we immediately began outdoor potty training.
I honestly find that mental stimulation tires Jackson out more than anything. Yes he requires a lot of exercise, too (even at almost 5yrs old), but trick training, or puzzle toys really tire him out mentally. If we don't get the proper exercise for the day, a 10 min training session with satisfy him to go lay down for a while. Especially pups, they get mentally tired out quick... work on some training... they can also get exercise in the process, work on 'come when called!' so he's also moving and learning at the same time.
Check out
Zak George - YouTube and
kikopup - YouTube for some ideas and directions on how to teach tricks.