We have allocated some of the duties to our staffs, such as the meal preparation, the space decoration..
There are specialized team staffs with the different responsibilities, like the meal preparation, the room interior,
Some of the job has been allocated to the staffs, like the meal preparation....
「全てをプランナーがやるのではなく」と言う文脈だと、「プランナーでない仕事は割り振られている」となりますので、"Some of the jobs/duties/works"は"allocated"されている、例えば、”meal preparation"とか。「ほとんど振り分けられている」場合は、”Most of the works have been allocated to..."となります。全文は、”(As planner is in charge of (the planning the party overall/プランナーはパーティ全体のプラン（の責任者だが）), ) It's not that all of the works are his responsibilities and some of them, like the meal preparation and the space interior decoration, have been allocated to the different staffs."
日本 
