What to do with Grandpa when he visits ?

My 86 year old Grandpa is coming to stay with my family for 4 days next month.He suffered a MILD heart attack last month but still is able to fly out.I hear that all of the meds' that he is now on ,have taken away some of his energy.He is a bit forgetful but in other wise good health for his age.We planned on going out to dinner and keeping things low key.Being that this may be the last time that we see each other what other activities would anyone else suggest? We live near Boulder Colorado.