Awesoming Up the Combat

My boys are instinctively interested in weapons and fascinated by all choices. While descriptions of swinging battle axes does a lot to reward their enthusiam, I feel I need reward their interest mechanically in the game, while keeping lightweight old-school-style combat. I like the Swords-and-Wizardry idea of using separate defensive, to-hit and damage bonuses for using a shield, two weapons and two-handed weapons, respectively. However, I also dig splintering shields, and figure that gives too much of an advantage to shields. Particularly when considering how fragile low-level characters are, the ability to cheat death for one round is too appealing compared with a mere +1 to hit. So I've adopted the following.

• Shields shall be splintered. After any attack, a character can specify that the shield took the blow. Non-magical shields are immediately splintered. Magical shields are splintered on a 1 from a d8 roll (for +1 shields), or a 1 on a d12 (for +12 shields). I may adjust those odds depending on how frequently magical shields show up as loot.
• Two-handed weapons do an additional 1d4 damage. Rolling more dice is fun! Also, if either of the damage dice roll the maximum (eg, a 4 on the d4 or an 8 on the d8 if a battle axe is wielded two-handed), the target is stunned for one round. Maximum damage on both dice does additional awesome at the DM's discretion. This doesn't apply to pole-arms, which have the second-rank bonus already.
• Wielding two weapons (one in each hand) means to-hit is rolled twice, with the best result taken. Which weapon to use for damage can be chosen. Only one die of damage is done, unless maximum damage is rolled in which case you can roll for the other weapon. Maximum damage on both dice result in awesome. Any magical bonus applies to both to-hit rolls, but magical damage bonus only applies if you use that weapon's damage roll. For example, if you're fighting with a short sword and +1 dagger, you roll to-hit twice at +1 each, and if you hit can choose either 1d6 or 1d4+1 damage. Some weapons are not suitable for two-attack use, depending on how the DM feels. Battle-axes and bastard swords are not, long swords maybe. Maybe the character's strength matters. We'll see what comes up.
• Spears and pole-arms may attack from the second rank. I've been strict about how many people can attack each other at once, as well as how many can fight side-by-side in a corridor, so this rule has come up a lot for Achilles, Theo's Greek-inspired fighter armed with a spear and a shield. Achilles has spent a lot of time poking additional attacks with his spear in situations that would otherwise be too crowded.
• Critical hits do either maximum or double damage at the player's discretion, and they can choose after they roll. As a youth I was traumatized by rolling 1 for damage after a critical hit. If the damage done is way too much for the opponent, like 9 hp damage to a 3 hp kobold, the DM can awesome it up, like arrows shooting through two enemies or similar mayhem. 

Thieves don't get the two-handed damage bonus. Magic-users don't use any of this.

I initially thought these rules were too over-powered, but have moderated after seeing how easily a 3HD mountain lion with 1d4/1d4/1d6 claw/claw/bite attacks could dispatch a party. Clerec the Cleric has horrific scars across his face and shoulder as a result of that encounter.