Take advantage of that high Charisma.
Divine Vigor is hard to beat for your 6th level feat. At sixth level you'll get 12 temporary hit points and +10' of movement. Move 30' when wearing your full plate!
At 9th consider taking Extra Smiting. By that point you'll have at least 18 Charisma. So, each smite will be made at +4 attack and +9 damage. At 10th level you'll be able to do this 5 times/day, which is plenty. Smiting is especially good during a charge with a lance.
Also, at 12 consider taking Power Attack. You'll have BAB to spare at that point, and power attack works great with a two-handed weapon. Again, it's especially good when you make a two-handed lance power attack while smiting and charging.

Assuming 12th level, 14 Str, and full power attack from a charging mount vs. an unmounted medium opponent, you'll attack at +9 and do (1d8+3+12+24) x 2 damage. That's 40-48 damage using nonmagical gear; add in your weapon enhancement, Str boost items, elemental damage, buffs, etc. and you'll crack 50 points of damage per charge--which means Fort-save-or-die for your opponent.
If you had taken Divine Might instead of Divine Vigor, you could add another 8 (4 x 2) damage from a use of that feat.
Of course, there are whole feat trees for mounted combat, including tacking on even more damage multipliers. If you're really serious, just search the WotC character optimization boards for "paladin charge". Those nuts have gotten to over 1,000 damage per charge.