Bannockburn was quite similar to Agincourt in many respects. Superior force gets stuck in the mud and cut to bits by better led army.
The Bruce certainly ensured that a trap could be set on the site by digging ditches etc. He was also prepared to cut and run the second things went sour.
More crucial to the battle, he was supported by several Scottish nobles that had put aside their feuding and general in-fighting to make a stand with their King. If Robert loses at Bannockburn (he's outnumbered almost 3.5:1), expect the nobles to depose him if he's not captured or killed in battle. Scotland remains in anarchy for the next few decades as rival families battle for the right to rule.
Edward would now have two choices - he can either recapture Scotland town by town, castle by castle or let the nobles continue killing each other and perhaps exhaust most of the claimants to the throne so that they have no choice but to swear fealty to England.
Edward also has political problems at home, not least with the Earl of Lancaster. A decisive victory in Scotland will give Edward enough clout to have Lancaster executed for treason and allow him to weather any storm that might come his way.
The King's main problem was that he relied too much on favourites. Sexual orientation aside, he didn't have his father's knack for making friends on his terms and allowed himself to be strong-armed and bullied. Isabella would still probably be swayed over to Roger Mortimer and ally herself with him and Edward will still end up being deposed as he can't be relied upon not to make the same alliances as in OTL. However, the situation in Scotland will be rather different and successive nobles might make more of an attempt to integrate Scotland into England - possibly through an earlier personal union as Edward Longshanks attempted with Margaret, Maid of Norway.