Limit the amount of quests a day to some number, maybe 5, and allow people to pick the rewards they want with reduced efficiency if you pick the same one multiple times, or no reduced efficiency if you pick "Random" for example:
Quest 1: Pick LP: 10,000 LP
Quest 2: Pick LP: 5,000 LP
Quest 3: Pick LP: 2,500 LP
Quest 4: Pick Random: Get LP from random: 10,000 LP
Quest 5: Pick Hunger Reduction: -25%
Now you can't do any quests for 24 hours
Maybe make some special reward only for picking random as well, like good gilding rocks, or bonus LP/XP/Hunger reduction for picking it