Camping is regulated and you will need to obtain an EOT licence to run a campsite. You could start here for info / contact www.greececamping.gr
The info for requirements for the licence are here in Greek (could be out of date - you can use Google translate to get a rough translation or use the above link for contacts) - https://www.dikaiologitika.gr/dikaiolog ... i-kampingk
It says ' For the granting of the Special Operating Sign to Camping Tourist Sites the eligibility of the land and the architectural study must be approved by the Technical Service of the local EOT CTP and the technical and
functional specifications as well as the criteria to be graded, according to art. 530992/1987 (Government Gazette 557 / B)' For the technical paperwork you would need a civil engineer. Many civil engineers do this and also can get the full details of requirements and apply for the EOT licence for you.
Be aware also that it mentions EU citizens & non-EU (after Brexit if UK citizens) may not be able to get this, or other business', licence (? first question for the lawyer/accoutant ).
Brewing beer is a seperate business and highly regulated. Some contact info here www.ellinikienosizithopoion.gr/?page_id=236&lang=en
In effect you would probably have to get licences for two new businesses, going through all the requirements and costs for each.
You would need to speak to a lawyer, civil engineer and accountant. The regulations and ongoing business taxes will make it difficult to set up and run .. and that's assuming you do it before Brexit if you are both UK citizens.