Thank you Cypher for getting back to me!
Our original plan was to put their main cage in, take the top off and put a ladder down into their newer cage and over a series of weeks just move their old toys/accessories. Since their cage is so small now, it shouldn't be too hard to scatter all the current bedding though. The new cage is arriving in a hour or two, which is super exciting!
I'll place an order for the fitch bedding shortly, the more bedding the merrier
As with the shavings, I think I'll just put it as a lower layer for now so it's used up. I think my partner is on the hunk for a glass dish at the moment to increase the size of their sand bath, so hopefully we find something soon.
I've been worried about the gaps too on the top of the cage since we have two indoor cats who have been very interested in the new girls, and I know it's going to be a temptation for them. I'm not sure yet if I'll need to mesh it on the top and also the bottom so the cats can't push down and the hammies can't push up.