You can always re-wash the negatives to deal with dust, dirt and oil etc.

Whatever you end up doing, I think you should get some archival flat scans from a dedicated scanner so that they may have another level of preservation.

In Sydney you can rent an Imacon/Hasselblad X5 I think it was (or a 939) for $60/hour, given the speed of which you can go through film on those things, it's very very good value for money. If you have a lot of film, it may be worth a road trip even over the border if there is a similar place over there.

The object here is to preserve the family photos, not an exercise in digital resistance, imho you need a new set of 'originals' for an extra layer of abstracted preservation. You can still get RA-4 prints from scans, which is how the overwhelming majority of RA-4 is done. It is also time to look at the archival quality of an RA-4 print vs archival ink prints designed for galleries (from a pro-lab or high end printer), ie; the important part is he family photos.