Just checked the leaflet that comes with the Frontline Spot on, it just says 'Avoid contact with the animal's eyes' then later on in the leaflet 'This product can cause mucous membrane and eye irritation. Therefore, contact of the product with mouth and eyes should be avoided'. Might be worth just giving the out of hours vet a ring just to be on the safe side, they may just say to bathe the eyes but you never know.
Anyway, just wanted to reassure you aswell that your little ones will be fine with their ops, especially if they have the head vet on the case.