Estates often have very long histories, being built up slowly, and often end up being divided out between individuals/councils etc. I think here 'main estate' or 'principal estate' is right - the composite nature (existence of secondary buildings etc.)is already implied in the term, and the translation is short and simple.

"The Main Estate - comprises the house itself and 4982 hectares surrounding it including the park and the villages of Baslow, Pilsley, Edensor, Beeley and Calton Lees. Most employees and pensioners live in these villages, which are wholly or part owned by the Trustees."
http://www.chatsworth-house.co.uk/learning/estatemgmt.htm

"A beautifully maintained gravel road serving access to about 10 waterfront homes traverses about 890 feet of the property isolating about a 3-1/2 acre tract of land from the main estate."
http://www.lakehouse.com/page-1011.html

"...it is recommended that as soon as five plus members live in a given geographical area apart from the main estate, they form a new household or chartered branch of the main household."
http://www.ecs-imperial.org/documents/pdf/AGENDA9-3-99.pdf