Is it okay to say let's skip this summer

My daughter has 2 children 14 and 11. My grandaughter is 14 and grandson 11. Every summer since they have been born I have paid for them and their mother and myself to go on vacation to various places. In addition my grandaughtr has spent one week at my house since she was 9 mos old and now the grandson wants to spend a week. But this year, I AM TIRED. I do not want to have to move my furniture around and then put it back when they come. I don't want to spend all the money I spend when they visit, and frankly, I no longer enjoy all our "adventures". I am broke and I am worn out and I will gladly continue to take them to a few places with their mother and pay for it, but I don't want to have to entertain at my house. Am I the only one who feels this way and is it okay to tell their mother no visits this summer? It really stresses me out.