What am I overlooking? What would worry you if I were coming to your class instead of theirs?
Nintendo Wii
An hour is a long time for a 4th grade demo… especially @ the beginning of the year. Some will need all the time, some will not. I would suggest that you have @ least 2 different levels of worksheets (hopefully not busy sheets) for those that need a challenge as well as those on grade level. For those below grade level I would suggest an aid to help read and follow with them the lesson you are presenting. I would also have some additional material for those that finish first that would keep them busy as to not bother those students still involved with learning.
Kids in year 4 have a shorter attention span than kids in year 7.Keep the lessons simple for year4s.