Overit I know just how you feel! I too find my GC's summer visits (always with their parents) utterly exhausting, and inwardly groan when they say they are coming. Reallocating bedrooms, changing beds, cleaning and organising meals for seven to eleven people wears me out. Add to that the constant noise and activity of children (and my own health issues) and it becomes a rather stressful week!
But you should not feel guilty about your feelings. You have been more than generous with your time, money and hospitality over the years, and your GC are old enough now to understand that as they're growing older so are you - but you're at the other end of the age scale and now have less energy to keep up with them. Your GC are old enough not to be upset by this change of circumstances. Some frank and honest discussion with your DD and GC is needed now. I'm sure your DD will understand, if she doesn't now she certainly will as she herself gets older!
You could suggest that they stay in a B&B or holiday let near you for a couple of long weekends so that you can spend time together but not have to disrupt your home for them.
I really hope you're able to negotiate mutually agreeable holiday arrangements so that you can relax and enjoy your GC's visits once again.
Can I use my bus pass on London buses?
Awwww, he is so happy to see me…..