You have received excellent advice from the previous responses. Keep Jackie's reply about patience close by during the year. It is so true. Wayne's suggestion about using Ten Minute Math is very important. If you can't get your hands on the Ten Minute Math Book this year, borrow the 3rd and 4th grade units to copy the Ten Minute Math Routines at the back of each unit. They are very appropriate for 5th grade also.
I would like to know more about the background of the incoming 5th grade students.
- Have they been exposed to Investigations in previous grade levels? - Is this the first year they will experience this type of mathematics?
- What units do you plan to use this year?
If this is the students' first experience, you may want to consider starting with a few fourth grade units. Some fifth grade teachers opt to use 4th grade units in their first year of adoption.
Best of luck. Keep writing about your experiences. We all learn from each other's experiences.