I think it depends on the relationship you have with the guest. My mom and MIL love to "be helpful," which usually means keeping me company while I clean or organize or cook, and/or playing with the kids so I can do said cleaning or organizing or cooking. So for us, its pretty much the norm. we have time for good conversation while working and we dont' usually shop. As long as your MIL is not the type to expect to be wined and dined and entertained all week, I think it sounds like a great plan!
loving my dh and our littles (dd ~ 11 yrs, ds ~ 9 yrs, ds ~ 7 yrs, dd ~ 5 yrs and baby brother ~ 20 mo)