Formal writing: "…for my colleagues and {I/me/myself}."?

Solution 1:

... for my colleagues and I

This is just plain wrong, especially in formal writing. You don't use the nominative case as the object of the preposition. Would you ever say "... a language course for I"?

Me didn't think so.

... for my colleagues and myself

This sounds like it should be better, but only because the corresponding uses of my lend it a bit of symmetry. It is actually a questionable reflexive use of the pronoun.

Collins has this to say on the subject:

Usage Note: The -self pronouns, such as myself, yourselves, and herself, are sometimes used as emphatic substitutes for personal pronouns, as in He was an enthusiastic fisherman like myself. The practice is particularly common in compound phrases: The boss asked John and myself to give a brief presentation. Although these usages have been common in the writing of reputable authors for several centuries, they may not sit well with many readers today. A majority of the Usage Panel dislikes them, though resistance has been eroding over the years. In our 1993 survey, 73 percent disapproved of the fisherman example quoted above. In 2009, only 55 percent disapproved of the same sentence. The Panel still finds the use of -self pronouns in compound constructions even less appealing, but here too the percentages have fallen over the years. In 1993, the John and myself example was rejected by 88 percent of the Panel. In 2009, 68 percent rejected the same sentence.

It is worth noting that a majority of the above panel still finds such uses objectionable.

That leaves us with the much simpler (and to me stylistically preferable) me:

... for my colleagues and me

Again, for formal writing, you simply can't go wrong with this. At the very least it will satisfy the fussbudgets, and the others probably won't notice anyway.