LG is no more good than NG or CG - and while paladins in particular will be extreme LG's, its better to represent alignment by a series of shifting focuses than a set of discrete blobs - a 'moderate' LG could be closer in alignment to a NG or LN or even true neutral than they might be to an extreme LG - think of it like a wheel. The alignment determines what spoke you follow from the centre, not how far along the spoke you go.
Most people would be fairly middle-ish if mapped onto the wheel, and so they might dip from actions typical to one alignment to those typical to another often - a guy who hates mornings might wake up CE if the builders are at it at 6 in the morning after a long nights drinking, but may mellow to LG after a coffee and a back rub from his missus....
LG does not mean lawful stupid. If your enemy will not or cannot repent then giving them the opportunity to escape or kill your friends isn't LG, its just stupid. Certainly any enemy who ignores a chance to surrender once, betrays you, etc, should not be given the benefit of the doubt the second time, in Br undead, goblins, etc quite likely had their 'chance' aeons ago - and having repeatedly proved themselves untrustworthy will be given a chance only by a paragon of righteousness or an idiot (no snickering at the back!)
LG means making sure that your actions support the community not merely your own desires, that your actions are socially responsible (get the warrant before kicking in the door), that you are proportionate (don't decapitate offenders for stealing bread) and fair (be consistent in applying the law), it means working within the community to better it, not riding roughshod over it. It does not mean soft, it does not mean nice, it may mean forgiving, but not forgetting.
So if planning an ambush LE might shoot first and offer the survivors a chance to surrender - if they surrender really fast; LG might have a single brave soul stand forth and command they surrender / depart without harming their target, but if the other chooses battle then the lawful part of LG dictates that you make the battle as cheap on the community as possible, and an ambush does exactly that - all of you stepping out to implicitly say 'you will lose, give up now' is simply a psychological tactic, good guys might do it more often than evil, but it isn't intrinsically lawful that I can see unless the communal code demands it.
Surrender on defeat is not lawful in my view, die free or live as slaves is music to the ears of any evil and many neutral folk, while good people would put far milder constraints upon captives, accepting surrender should be fine for anyone - the good guys just feel more remorse over a slaughter.