This 生物 is read なまもの and means "raw, fresh, green" though this word is also read せいぶつ as "living things". So it is need to be eaten soon. About this ですので, Since this sentence is written for consumers in very polite ways to say, the first part is also need to be written in formal way. Between friends or close people, saying なまものなので/だから、はやく食べてね/ 食べてください is good. Though it's not very bad saying 生物なので... お召し上がりください but it sounds unnatural to us because of the balance of (the politeness of) the first part of the sentence and the second one. I hope this was helpful.

分かりました。ありがとうございます :)

生物は「せいぶつ」ではなく「なまもの」と読みます。意味はrawやraw foodです。 文章の意味から、読み方を判断します。 生物なので、と、生物ですので、は同じ意味ですが、生物ですので、の方が丁寧です。