First of all it's such a shame that this little boy's mum is changing her son's routine and that of the rabbit's to have her boyfriend's dog. Perhaps she could consider adapting their garden to house a shed and pen for the rabbit. It is so very kind of you to want to help out but It sounds like you don't have a lot of room either way! However, the rabbit would be fine inside a good sized shed or a large hutch outside with an area for him/her to exercise. Rabbits are very good at being house trained and will use litter trays in a shed as my own rabbit does. He has lived for the last 8 years in a 7ft shed that contains a 6ft hutch with a ramp that goes down to the floor of the shed. He has adopted the hutch as his bedroom. He has woodshavings and hay on the floor and in his hutch. A small oil-filled radiator secured to the top of his hutch, with nothing around it, keeps him warm in winter. He has a radio on in there (we get through a lot of batteries) and it's tuned in to classic FM. The shed has a tunnel fixed with a door that opens up into a 10ft pen (chicken wire and wooden frame - which my husband made, and covered over with bird netting to keep out cats and dogs). We encourage him into his shed at night and fasten the tunnel door to the pen because of foxes. He has buckets, boxes, ramps and baskets in the pen to play with, but most of all he loves his shed, especially now he is getting older. Your step-son's rabbit would soon adapt, but he would feel very lonely out there on his own and would need lots of visits, attention and grooming. I would not advise keeping a guinepig with the rabbit, particulary as the rabbit has been used to being on his own with human company. Rabbits can give a good kick with their strong back legs and guinepigs can get badly injured accidentally. I'm just wondering who will be looking after the rabbit when your step-son is at his mother's house? I'm guessing he will only perhaps be with you and his dad at weekends.