To help us provide a full answer, I wonder if you could clarify whether you hold any tickets already, when you intend to travel and whether you hold (or could hold) any railcards?
An nnetwork daytripper is not valid to Great Malvern even with an addon.
A West Midlands Day Ranger is valid but more expensive.
If you don't plan to go anywhere else an off-peak day return will be cheapest and easiest at £9.30 per person (adult, no railcard)