Melbourne Royal Childrens Visit from Cairns

Wanting some help my son has appointments in Melbourne at the Royal Childrens Hospital at the end of November and Ronald Mcdonald House while a wonderful organisation can not let us know if we have accommodation till the day we arrive and with two young children with me this is not an option does anyone know of any other organisations might be able to help of cheap self contained accommodation near the hospital my eldest will be four and youngest 5 months, the first week are just appointments but the 2 weeks my eldest will be in the hospital but unsure if i can have my 5 month old with me. Any help would be greatly appreciated