You can use a magnet to find out if your front forks are steel, but I still wouldn't do front motor. A little more work and any risk is avoided is how I look at it.

I have several rear wheel motor kits and one mid drive kit. I use the mid motor (BBS02) to occasionally tow a light cloth trailer with a 35 pound grand kid. My problem is not feeling any weight behind me, so I need a mirror to make sure the trailer is still there. While my trailer/load is under 100 pounds, I'm heavier, so I suppose my cargo approaches 300 pounds too. At the same time, I tow at bike speeds, so it's not about having power. I could do it with a 500w hub motor.

However, if I were to build a bike for my son to tow my grand daughter, it would be a mid drive. A little more money, a little more work and it makes for a better bike.