Consider the situation where I am handling a project, and now my manager assigns me one more.  
So I want to express to him that it will be hard work. I am in software, so taking on two projects will require more hours of sitting.  
I thought of the following ways to express it:
1. With the two projects, I will be burning candles at both ends
2. With the two projects, I will have my nose to the grindstone. 

I am trying to use idioms here. Are they correct usage?  
Any other way to express the same with impactful words