No. The Canter engine is very noisy and disruptive compared to a genny (esp if you are sitting in/near the EC!!) and you need to run the engine at fast idle (at least 1000 RPM) to push much into the batteries, and at this level you are chewing through a large amount of fuel compared to the gen. I can run the gen for 2 hours (say) and put in 80 A-hr to the two house batteries using just over 1 litre of fuel. To do this using the engine would be (guessing) around 10 litres plus of fuel. So if you had to do this 4 days running (bad weather, not driving, or just parked in shade) that's not only the cost of the fuel, but the extra fuel to carry.
I have used the engine once or twice to charge the batteries when desperate (before I had the genny). Not an option unless an emergency.
I guess if you "never" plan to run the house batteries down, so you only need to use the engine once or twice a year to charge the batteries (when your plans have gone haywire), then it would be an option. But we use the genny probably once a month, and sometimes for a few days in a row, e.g. we are in a nice place, by ourselves, parked in full or part shade, want to catch up on 'work' stuff etc. I run the genny for an hour or two in the middle of the day. Minimal inconvenience, noise, etc.
I should also mention that the 115 A-hr house batteries (or any rated battery) is only when the battery is brand new. As they age, their capacity reduces. The rated capacity of these batteries is to 10.5 volts and I never run them that low. If you are working to a self-imposed limit of "50%" of the capacity before topping-up, that might be 55 A-hr (50% of 115 A-hr) per battery when new, but perhaps only 30 to 40 A-hr when the batteries are 3 years old or 60 to 80 A-hr for 2 of them (and you do need to have a viable, robust solution for when your batteries are aging not just when brand new). So if your (aging) batteries are full when you pull up to camp late in the day, and you are drawing about 30 to 40 A-hr per 24 hrs for the fridge (depends on weather), and a few A-hr for the water pump, lights, etc, then if you run 2 laptops for 8 hours each at 3 amps (24 A-hr each for the day), you have run out of puff (say 90 A-hr used) in less than 1 day. Even with new batteries, you get only 1 full day out of them if used this way.
If you then look at the tables of peak solar sun-hours per day, then in perfect conditions, in Australia we would get about 60 A-hr per day out of 3x68 watt solar panels. Now factor in partial cloud or shade, heavy dust on the flat EC roof's solar panels (who keeps them clean all the time?) etc, and you will be under that value. So even with only one "layover day" to do computer work, you may need some non-solar power input.
Rick