Perhaps the best way to describe the "Elohim/elohiym" is the "One God" has many "sons"; the result of God's creation of those who bear His image and likeness.
Jesus illustrates this in John 10:34,
Jesus answered them, Is it not written in your law, I said, Ye are
gods? 35 If he called them gods, unto whom the word of God came, and the
scripture cannot be broken;
36 Say ye of him, whom the Father hath sanctified, and sent into the
world, Thou blasphemest; because I said, I am the Son of God?
This is taken from Ps.82:6-7 which says,
I have said, Ye are gods; and all of you are children of the most
7 But ye shall die like men, and fall like one of the princes.
To be "elohiym" is to carry immortality, which is a function of the spiritual creation that lives forever. This is the destiny of every created spirit, to live forever in the presence of Elohim.
Ha-Satan(the Opposer) was created as Lucifer(the Light-Bearer), however(Isa. 14:12-13) says,
How art thou fallen from heaven, O Lucifer, son of the morning! how
art thou cut down to the ground, which didst weaken the nations!
13 For thou hast said in thine heart, I will ascend into heaven, I
will exalt my throne above the stars of God: I will sit also upon the
mount of the congregation, in the sides of the north:
In Ezek. 28:14-15, it says,
Thou art the anointed cherub that covereth; and I have set thee so:
thou wast upon the holy mountain of God; thou hast walked up and down
in the midst of the stones of fire.
15 Thou wast perfect in thy ways from the day that thou wast created,
till iniquity was found in thee.
God had created "sons of God/angels"(elohiym) as immortal beings who would manifest His Glory in Heaven, and (Heb. 1:13-14)
But to which of the angels said he at any time, Sit on my right hand,
until I make thine enemies thy footstool?
14 Are they not all ministering spirits, sent forth to minister for
them who shall be heirs of salvation?
The fact that "Lucifer" became "Satan" did not exclude him from being a "son of God", although as Ps 82 states, "ye shall die like men, and fall like one of the princes", the "prince" here specifically refers to Satan, who was cast out of Heaven, and ultimately sent to the Lake of Fire reserved for him.
Hell from beneath is moved for thee to meet thee at thy coming: it
stirreth up the dead for thee, even all the chief ones of the earth;
it hath raised up from their thrones all the kings of the nations.
10 All they shall speak and say unto thee, Art thou also become weak
as we? art thou become like unto us?(Isa. 14:9-10)
To Answer the Question
The text in Job 1:6 is not clear as to who was and wasn't invited. Obviously the "Opposer" cannot be seen as one who is obedient to the Will of God. But that didn't exclude him from being an "elohiym"; albeit one who will burn forever in the Lake of Fire, although in this dispensation is "as a roaring lion, walketh about, seeking whom he may devour(1 Pet. 5:8). For God to 'permit' Satan to have access to Job, it had to happen within the boundaries established by God, which were outlined in the rest of Job 1 and 2. Satan, who was cast out of Heaven, along with his angels(Ezek. 28:17/Rev. 12:9) does not walk in the counsel of God. But he is allowed access to men, as seen by Job, and also in other circumstances (1 Kings 22:22) to fulfill a particular purpose, and that is how we must read Job 1:6.