I am a member of a Facebook group 'Yoto Fans UK'.
Within this group, a recent topic of conversation was the poor selection of Cards in the Yoto Club. A lot of members have commented on how they left the club after a few months due to poor selection and news ones not being added regularly enough.
You should consider having a selection for various age ranges and also more introduced every month to keep people in the club.
You could even consider adding 'Make Your Own' cards for when people don't find a card they want.