My in-laws r planning a europe trip and after that for some days they wish to go to US to my brother-in-law.?

But my brother-in-law and his wife are very diplomatic. they wish to say no to them but since they can't be upfront so they are asking them to postpone their US plan for a couple of months. But my in-laws are old and can't really travel again and again. So should they at all go to US?