I have done it many, many times and several before cell phones! It is helpful that you have the 5 yr old they can be a big help with the 2 yr old, handing them things, talking, etc.
Have books on tape (Cd's now) take snacks so you don't have to stop all the time, learn to "hold it" so once they nap you don't have to stop till they wake up. My kids weren't morning kids so I would try to hit the road at like 5:30 or 6 so they would sleep for a couple of hours and I could get some good miles in.
At lunch find a McD's with a big play place and let them burn off energy while you sit and regroup. Take some new little toys so they have something new to play with when they get restless. When portable DVD's came out they were great cause they could watch a 1 1/2 hr movie without complaint.
Expect some days to go smoother than others and be very clear with what they need to do and when. For us it was we don't stop going thru Chicago! so before I announced the last rest stop and they learned from 2 on to go or wait till Gary! Or have the older one dig out change if you forgot a toll, which reminds me have a bunch of change and ones within easy reach for tolls.
Just use common sense and plan on it taking a bit longer.