Took in a stray. What to have done at the vet?

I took in a pregnant stray 3 days ago. Yesterday, she gave birth to three fuzzy little marshmallows! Well, burnt marshmallows. She and all three babies are tuxedos. The day I caught her, I called all the shelters and they either could not or would not take her (out of district).

My SO's father wants to take mama and all 3 babies in to the vet to make sure they're all healthy - so, exams (x4 = $160 to start). That's obvious. I don't think, unless anything is wrong, there's anything else to concern myself for with the newborns right now. But what about momma cat?
All I know is I want to get her tested for FIV/FELV. Spaying, obviously, has to wait... nor are we likely doing vaccines or anything just yet.
**This will be done by us IF we decide to keep her; whether or not we will is unclear right now. She's staying at my SO's brother's home in a spare room as my SO and I live with his parents. His dad is on board but his mom doesn't want a 4th cat in the house, but he says she's getting so attached she might change her mind. Momma is a total sweetheart.

In any case, his dad is wondering if we should ask for bloodwork, xrays, etc. etc. anything. If anything is really necessary I'd like to think the vet will say so BUT to be honest I don't know which of the 3 working vets will be there. My family loves one vet but hate the other two because their advice in the past has been horrible. So at the same time I don't want to get talked into unnecessary procedures either.

I would do nothing in terms of vet as long as she and babies appear healthy.  If you get a leukemia test now, you would still have to repeat in a couple of months because she could have been exposed right before she came to you.  Also, if she tested positive, then you would have to consider removing kittens from her and bottle feeding them to prevent them from getting positive from her milk.  As an experienced rescuer, I think Time Will Tell is a good way to handle it, not to mention saving money and avoiding exposing her and the babies to any bugs in a vet's office!  If the babies do well and everyone seems healthy, the most you need to deal with is making sure she has no fleas because the fleas will migrate to the babies and will multiply.  Save the vet money for illness care if you need it, and hope you don't need it.  If you were to vaccinate her now, you would have to use a killed vaccine, and most vaccines are modified live vaccines.