There are some Tasmanian Records on FamilySearch see: https://familysearch.org/search/collection/location/1927080?region=Australia
http://findmypast.com also has Tasmanian birth records 1803-1933 but I couldn't find any entries for your grandparents.
You could also try https://www.linc.tas.gov.au/
I couldn't find anything on your grandmother, but I found your grandfather's will, which you can download here: https://linctas.ent.sirsidynix.net.au/client/en_AU/all/search/detailnonmodal/ent:$002f$002fNAME_INDEXES$002f0$002fNAME_INDEXES:702303/one?qu=edward&qu=roy&qu=ferguson
There is one article on TROVE for a Memorial Notice of Freda HINE (nee SAVILLE) who appears to be your grandmother's sister http://trove.nla.gov.au/newspaper/article/68362935