Can I set up S3 to use some kind of 2 factor authentication?
No, because S3 doesn't have authentication of its own.
Does the Access ID count for 2 factor since it is random and not tied to a person's name or anything else?
No, the factors in "two-factor authentication" are different types of things; usually for 2FA it's something you know (a password, a secret key) and something you have (a hardware OTP device). The reason multi-factor auth is so oft-recommended is because it's difficult for an attacker to gain access to both types - a physical thief can steal your phone or keyfob, but won't know your password, and a remote attacker can steal your password or secret key but won't have access to your OTP device.
In addition, Amazon key/secret key pairs are the sole thing you need to access the AWS API (you don't need to know the user's name), so it is not only not a second factor, but is the only factor.
As a first step, it's a very good idea in most cases to enable S3 bucket versioning. This will store old versions of files, which increases your storage costs, but can be a lifesaver if you accidentally delete something important.
In a single Amazon account, you can create sub-accounts and manage them with IAM. This is generally how you should manage multiple users, rather than giving them all shared access to the same account. With IAM, you can add the minimum necessary permissions for each user by assigning the appropriate policies. Thus, if a client needs to be able to read protected files, but doesn't need to write to them, you can give them only read permission - and thus, any breach of their credentials will only give the attacker read access. Similarly, you can provide write access without delete. You can also scope S3 permissions by filepath, and generally have a lot of flexibility to target precisely what you need.
