I'm glad you're taking a break. Be sure to bring back pictures.
Telling your mom that you'll be gone is a judgement call. Does she seem to get agitated when you leave after a normal visit?
By all means let the staff at the home know. Supply alternate emergency contacts, or make sure they have your cell. They might also have an idea how much to say to mom.
Does she remember who your son is? I'm inclined to mention it, something like "today is Tuesday, and I'll be back again a week from tomorrow on Wednesday the --," or some similar. We keep a calendar in Mom's room and mark important days for her to look forward to - mostly visits from my sibs and holidays. But my mother is only 84 and is used to me skipping a few days between visits. We do have a rather sappy good-bye ritual at the end of each visit.
But it is a judgement call. You just have to do what you think is best for both of you. Then go have a good time.
Happy Mother's Day! Have a safe trip.