help! baby won't relax at grandmas!

My daughter is about 6 weeks old and plan is for my parents to keep her when I go back to work in January. We see them a couple times a week, almost every visit is at their house. However, my daughter WILL NOT nap at their house and is pretty fussy when they hold her and try to soothe. Also, my dad has some mobility issues and tries to soothe her without getting out of his LaZBoy. Apparently I was the worlds most quiet baby and never fussed, so neither of them really know what to do when she gets fussy. Also I was a baby 34 years ago. I try to gently instruct them and tell them what she likes at home but they really seem perplexed by her behavior. My poor dad seems to even be starting to take it personally ("aw...I guess she doesn't like grandpa"). I'm so worried about when they start watching her full time - how is everyone going to adjust??