Ditto on the above.
The golden is more than old enough to allow for a second pup, and it is always good to keep them separated ANYWAY until they are old enough to be around "distractions" like other dogs - even in your own home.
There is no reason you can't have both. Separate crates, rotate who is out.
Even if you did NOT have the golden you would need to keep the GSD crated at times throughout the day - whether you are there or not. It is VERY important that the dog not think that just because people are home, it no longer needs to be in the crate.
A sample schedule:
Wake up, take dogs out, on leash, one at a time (puppy first due to lack of bladder control and housebreaking etc)
Both dogs in crates, have coffee, whatever
Take pup outside, big game of whatever, tire out pup, back in crate, feed
Take Golden out while pup is eating, go for a brisk walk, maybe a game or two or a short OB session. Back in crate, Feed
Take pup out to pee etc ONLY, then back in crate, remove bowls.
get kids off to school, etc breakfast
get ready for work or day, shower, etc
Take each dog out separately to pee again
Go to work, errands, or sit down at home, do yard work etc
Come home/finish up whatever you are doing at home, put stuff away, etc. I don't know your schedule, but if you work and come home for lunch then this would be a good time to do this:
Take dogs out to pee, pup first (again because of bladder issues not anything to do with rank, etc)
Play with pup, maybe a little luring with treats to start teaching basic OB commands that will be taught more formally later, back in crate
Take out Golden OB session, maybe a walk, etc Back in crate, or maybe keep tethered to you for a little while around the house, then crate
Take out pup, pee, then maybe have tethered to you in the house for a little while, then back in crate. (Having the dogs on leash here is if you have the time. If you are on lunch break or whatever you may not, so just a quick potty break, short play time for each, then back to work.)
Come home (if you went back to work) Quick potty break for dogs, back in crates, get kids taken care of, take care of dinner, carpool, kid activities, whatever
Take out pups one at a time, little OB, maybe a walk if there is time, feed (and potty again, at least for the pup)
Dinner (dogs in crates) clean up, get everyone settled with evening activities
Potty break for dogs, take out one of them for a tethered time out of crate, maybe a walk for the Golden, then tethered time for pup, etc
Take pups out one last time before bed, put them in crates, go to bed
There are no times or anything like that on the schedule because it isn't really necessary that at 5 pm sharp the dogs are fed, 6:35 they go for walk, etc.
Just have a general schedule that is more or less structured in sequence, not time. Vary as the pup grows, and on days that don't apply to this (like weekends, etc.)
One day the dogs may be crated for 4 hours after breakfast, then next for 30 minutes. It just depends on the day and what you have planned.
Since you really don't have to worry about the dogs being anywhere near one another for a while, it really won't matter that you have a golden and a GSD. If no one is wanting to take care of the golden, then maybe consider training it and working with it yourself, to show your sig. other and his daughter the responsibility needed to own a dog. It may help prevent a fight as well, and still get the message across.
Plus, you can do some of the activities with the golden to learn yourself: like the OB work, the tracking, etc. Sometimes it helps to learn on a softer dog first, then you will be more experienced when it comes to the GSD
JMO
When a flower doesn't bloom, you fix the environment in which it grows, not the flower.