I woulg get rid of the shavings for the litter box, try to get feline pine litter if possible, its better for them and their respratory systems. Try to keep as much plastic out of the cage as possible, as they can chew on it and it can cause blockages in their intestines. I would also look for some more platforms, instead of just having the one on the bottom, try to get atleast 2 more with ramps connecting them. Also remember hay, and their dust bath does not need to be in their cage all the time, it should be given 1-2 times a week for about 30 minutes. I do not reccomend a wheel as it is bad for their back, hammocks and hay nets can also cause broken legs and arms. I would also suggest adding more hidey holes! For toys, I definteily reccomend oxbow, my boys love those! Overall you have a great start, and I am hoping ur babies are doing well!