Let me first compliment you on proactively starting this initiative of sending motivational inputs daily to your employees. You also deserve kudos for identifying the problem of boredom, realizing the impact of your initiative and the motivation given by employee feedback and most of all for working out a solution to your problem. It is equally important that you also solve the issue of some employees not receiving your inputs.
You have outlined a possible solution which to my mind is an excellent one. My suggestions for you to explore further options are as under:
second motivational input can be shared on Thursday instead of Tuesday and shift the Thursday input to Tuesday.
2. It would also help if you can have some broad categories for the week so that all inputs be it a motivational input or a joke or puzzle relate to that category. These categories could be based on functional activities like production, marketing, finance etc. or based on themes like environment, team building, quality etc.This categorization need not be shared with the recipients but is merely to help you identify the right inputs for the week.
3. To get more inputs without straining yourself, you could enlist the support of some of your colleagues who give you positive feedback to share inputs they have got from other sources. The best way is to find out if any of them could also volunteer to work out the inputs for the week based on a theme. eg. you could get a person from marketing to prepare all inputs for the week related to marketing. It is very important that you give credit to the person contributing so that it motivates her/him as also others to volunteer.
4. I would also suggest that you have a stock of material for a month in hand so that in case a volunteer is unable to contribute on time or you are on leave or run into writers block/ sourcing block you still have inputs to share.
May I also invite you to visit the following Inspirational and Motivational blogs which could also provide you some additional inputs and trigger fresh ideas and perspectives for you to explore
It is a valid point that people should be involved and be a part of any programme to get success.
So atleast once a day make it for the employees.
Call it Your own contribution day.
In case no one comes forward you can always fill in the gap.
Give recognition to those who contribute.