LeeG

You can probably keep your front wheel if it's true and un damaged , get a new rear wheel with 36spokes and any pick of rims and spokes depending on your budget. 32mm are fine for your load on pavement. The weight you're carrying will give you a lot more work going uphill, your aerodynamics will limit you downhill. The type of tire will make a bigger difference than 32mm or 35mm wrt effort but it's still a smaller factor than weight and the motor.
If in your shopping you come across a good deal with straight gauge spokes don't worry that they aren't double butted. You're more likely to wear out the rim or damage it in a crash before spokes start breaking if it was made right the first time.

i like putting heavier/tougher tires on the rear if it's carrying a significantly greater load than the front. While the heavy tire is noticeable on an unloaded bike the difference kind of disappears with a load. In addition to the tires mentioned above I like the Panaracer T-serve. There are tougher tires but these ride nice with adequate durability and puncture resistance. With a pannier load I't put a T-Serve in the front and something heavier in the rear. The tread isn't that thick on the T-serves. Except for the Schwalbe Mondial I'm not a fan of deep sectioned tread like the Continental Touring models. I'd rather have a thick smooth rubber tread than a deeply sectioned one.

Rivendell Jack Brown Blue is a nice tire, that in the front with a Conti Gatorskin Hardcase in the rear would be a smooth rolling and durable setup .
A 35mm Mondial looks about the same size as a 32mm tire, it's a good choice for long tread life on the rear.

btw a front generator will use up much more energy than the difference between a 32-35mm tire.