Congrats on you future Suggie parenthood and Welcome to GG!
Yes, having Dad neutered as soon as possible is best, there is a chance they could mate again and you may have 1-2 more joeys coming.
Since they will be new to you they will need time to adjust to you, your homes sites, sounds and smells too so you just want them to settle in and get used to everything.
I took home a breeding pair last summer and they had 2 joeys IP that came out 11 days later. I had the Dad neutered on day 13. I put him right back in with his family and he was fine. It's less stressful for them to stay with their cage mates. He will be a bit sleepy and probably not to active that first night after surgery anyways.
I didn't try to handle Momma because she was(still is) pouch protective crabby, so I didn't want to stress her at all and risk losing the joeys.
If they are willing to let you hold/handle and interact with them, you can. Just as long as it doesn't cause them any extra stress...if they are used to that than you can keep doing their routine.
If she is already nursing a joey(since he/she is not weaned yet)...they may be feeding her a different formula, giving her extra or giving her more protein.
Which HPW are you going to be using...there are many versions.
Some will just offer an extra serving of the staple,fruits and veggies so Mom can eat extra if she needs to.
My pair came to me eating the Glider Kids Reduced Honey version diet with extra servings so and I wanted to keep everything as familiar as I could for them.
I gave Momma a bit of yogurt(vanilla or strawberry, the regular kind without any artificial sweeteners), mealies or Gerber chicken baby food as a protein snack everyday before they went to sleep and I went to work for the day.
I still wanted her to eat as much of her nightly food as she needed.
Also if they do have any male joeys, you will want to separate him or have him neutered at 12 weeks old.