Have them use a bed or sleeping mat (there are several in the army camp near the north gate waypoint in Cyseal, for example).
Beyond Divinity and D:OS 2 have portable bedrolls, but there aren't any in D:OS EE.

There are also spells to heal, or food/potions/scrolls (but I'd keep consumables to use during combat, and stick to magic otherwise, where you only need to wait for the cooldown).