A 45-minute album takes about 108 MB on High and up to 476 MB on Lossless (sample figures).
For a week away, 40 albums on High fit in about 4.3 GB. Download over Wi-Fi the night before, and open the app once while you are still online so the licences are fresh for 30 days.
Tip: turn on Downloaded only in the Library, so the app never reaches for mobile data by mistake.