You're right, a creator licence is fine for mobile apps. But how do you intend to get data onto collector without agol credits? I don't believe Collector supports MMPKs but Field Maps does. However, you can't edit data in MMPK so is only for reference.
Without authoring the web map in AGOL, you can't get an offline map into Collector. And you'll need credits to host the vector and tile data in AGOL.
My advice is either switch to field maps and MMPKs (requires an arcgis pro license) if you're not editing. Or purchase a small amount of credits to host vector data in AGOL, and then use one of ESRI's offline basemaps.
David
..Maps with no limits..