Is there a membrane beneath the gravel, Jimbo? If so, any weeds will be very easy to pull out with your fingers and there is no risk of getting spray on your plants and lawn.

Pathclear does what it says on the tin so to speak. but if it gets onto the plants you want then they will die.

There is usually a watering can option with weedkillers - the concentration is different but there is no danger of wind drift and none of splashing onto wanted plants as long as you are careful.

There is a granular weedkiller that you scatter on to the paths - it works for about 6 months, but i don't know the name.