Sometimes it is hard to know what is best. How will you feel if you leave without letting her know you will be gone for a short period of time? I think, perhaps, that you will worry because you didn't say something and that might spoil your visit... On the other hand, if you think it might worry her, then perhaps it is best to say nothing. However, if you mention it to your mother in a calm fashion and reassure her that you will be back soon, then that will take that concern off of your mind and may not cause her too much worry.
You deserve to have some time with your dear son. Try to go with a clear conscience. Take a moment and sit down with a cup of hot chocolate and relax. The answer will come and follow your heart.