It is unclear from the question whether the acquisition falls under Architecture-Engineering Services. If it does, then the answer is clear. Per FAR 16.500(d) the statutory multiple award preference implemented by FAR subpart 16.5 does not apply to architect-engineer contracts subject to the procedures in FAR subpart 36.6.

In all other instances, the FAR does allow for the contracting officer to apply some judgment when it comes to multiple awards. FAR 16.504(c)(1)(i) does “encourage” you to use a multiple award under a single solicitation but does not require it as it uses the term “to the maximum extent practicable.” Unfortunately, we would need to understand more of the specific circumstances of the submitter's question to provide more insight on whether a multiple award IDIQ would be more appropriate than 3 separate IDIQ contracts.