The cage size is fine. I would look at getting them a wheel - one of these is ideal rather than a plastic one which they would chew to pieces. I don't like the look of the hammocks though as a chinchilla could so easily get a leg trapped in those. Try Hammocky Hammocks instead for something more suitable. There is also the Fuzzbutts site as well.

With your sandbath, just put it in for an hour every couple of days or so and take it out again. That will stop it being used as a toilet which could encourage disease. They do not need hay on the bottom uner the wire floor either, newspaper is quicker and easier to keep replacing and won't harbour mites and bacteria as much as hay underfoot will.

Some chins like to be handled and others don't. I have one who hates it. I worked on him for a long time by making a deal with him. If I get to touch his back, he gets a daily titbit. He won't come for fuss but at least he does not have a screeching fit anymore when I have to catch him. I do not handle him unless neccessary though. I cannot make him like handling so why stress him out? I have been able to take him to a vet and he did accept examination though.

To catch chins without stressing them when you have allowed them free play in the room, get a 'Chube' or a piece of cardboard carpet inner tube (many carpet shops will let you have those for free as they only have to pay to dispose of them and they make great toys for them to play in and chew up) and place it on the floor. Persuade the chin into it, pick it up and gently tip chin into cage or put the pice of tube in anyway! Chins love to chew stuff up so plain cardboard and toilet roll tubes etc are much appreciated, the latter can be stuffed with hay for them.