ORIGINAL ANSWER: How about: “Please get in touch directly with me (preferably) or my colleagues if I am unavailable”?
EDIT: now that I understand what the OP is asking about, I no longer think the change I suggested above is necessary. The original sentence is fine. Here is what I said in a comment below:
“Me and my friends” sounds juvenile when it’s used as a subject, because it shows that the speaker doesn’t know the difference between subject and object pronouns. As an object, though, it’s fine- “my friends and me” would usually be preferable but the reverse is not wrong. Likewise, “me or my colleagues” would sound juvenile as a subject but not as an object. The order of words here is fine (“me” first) because you want to emphasize “me” as the preferred contact. (To be clear, I am talking about your original sentence.)
"Please get in touch directly with me or my colleagues" is perfectly correct and "mature" English. Putting "me" first in the sentence (before "my colleagues") is sufficient if you want the person to feel free to contact you or else any of your colleagues if you're not available.