Hi John,
You have some serious focal length there and assuming you have a eq6 mount with goto, make sure you drift align well and if you have time before imaging each target do a PEC run..I don`t know how long you will get and the number of bloopers to good pics will be but the shorter the better, with my setup (850mm focal length) with 1min exposures I might get 80% good then with 2min maybe 40%. Any more than that its just good luck...So I would stick to the brighter targets like m42,eta carina, m8 or mcnaught. Don`t try to do too many things in a night and just work on the brighter ones..and keep to 1 min or less. By all means try some longer ones you never know..
If you know how to use and take and process dark frames I would recommend turning off noise reduction since you only have 2 batteries, you will be using half your reserves just by letting the camera remove noise even with the bloopers. You should get close to 2 1/2 - 3 hours before you run out off juice, depending on the temp etc...
Good luck and hope you nail a few good ones......
Cheers Gary