With 4 DCFCs his charge rate may drop due to heat which may stretch out the trip more. If you are adventurous (my wife is) and have time to burn go for it but otherwise I'd rent. the new LEAF Plus would only need one DCFC for that trip no problem at all if you want to buy a new LEAF
If you drove slow and efficiently enough a Plus may not even need to be charged at all but I wouldn't suggest risking that.
I am pleased with a Better Route Planner, it is a great planning tool. You will also want to check plugshare BEFORE you leave so you know if the chargers you need are healthy based on checkins. In a better route planner make note of max speed, the faster you drive the less range you have. Air conditioning also can lower it a little. If you are really paranoid like I was when going hundreds of miles for a little while I got power cruise control, that is like a better route planner but uses an OBD II and gives you real time feedback on if you will make it based on how you are using energy. I am amused by it but most of the time A Better Route Planner is actually just fine as long as you pay attention.
I just want to mention again check plugshare as well to see if the chargers most recent checkins look good.