Hi.
Due to real life commitments, not all guild members are able to log in AND complete their guild quest every day. Therefore I would suggest reducing the number of members needed to complete the quests to achieve the maximum combined reward. Players would still need to complete their part of the quest to get both the individual and combined amount, however it would reduce the pressure on many players to do this EVERY day, whilst allowing those who do complete them to be rewarded appropriately.
I believe the maximum reward should be received with only half of the members completing their quest. Those who do not to take part on that day will not recieve anything, meaning all players have a reason to get involved where possible.