In my experience, one thing that is critical is to stick to the routine with kids. It will help you and help them. With the infant is easier. With older kids, naps and bed time schedules are a must! Also, no candy at least 3 hours before bed!
I had the girls, 2yr 10mo and 4yr 5mo, for 13 days by myself a few weeks ago. My biggest fear was sickness. They got sick, but luckily for me, a few days before mommy was coming back, so I just had the last few days of complete chaos.
I find that it is fun to relax a bit the norms, but not too much. Ben may be too young to recognize this though. My 4.5yo is quite the button pusher and will most definitely try to push boundaries.