I think it might be nice if rather than shards, daily activities reward a full moonstone. There can (and should) be a cap, even if only one FULL moonstone is guaranteed and the rest is pebbles or sometimes shards.
With the actual daily activities- to encourage and reward people for playing each day even if they don't have a lot of time, one MS might feel a lot more tempting than trying to get 10 shards. Even if it's just completing that one single task that grants you a full MS that you don't have to craft.
To clarify, I do not mean each individual activity. It could be a reward for completing all of the daily activities (and these could be made finite, but more rewarding- rather than seemingly endless) Or could be completed in sets, and the first full set gives the bonus MS, and the rest give just pebbles or possibly some shards, just throwing ideas here.