E-350 as a tow vehicle?

Better to let it rev rather than lugg. Drop,it down to third or even second when necessary. You might need to let your speed drop a bit on the inclines. Don't overwork it trying to maintain. Watch your temperature gauge. If it's climbing it means it's working too hard. Drop it down a gear and rather than push it too hard. Consider 60 or 65 as your max speed. With a family of eight is is going to be very easy to accumulate weight! Be careful of that. I've learned.... It will take as long as it takes, burn whatever gas and oil it uses, and cost as much as it costs. It's the price you pay for fun and adventure!!! Be safe! Travel well!