It is probably better for the Sorcerer to take Craft Arms and Armor, since it requires skill ranks in Spellcraft, something the Sorcerer probably already has.
A paladin's mount can be a powerful option with it gaining some energy resistance, DR, and Spell Resistance at later levels. Just make sure at 7th level when you can get 2nd level spells, grab the spell Shield Other to help your lion tank better.
A lion animal companion will be a big boost to combat especially with all the extras a paladin’s mount gets, but there are some downsides to it. First and most importantly is that it becomes large at 7th level. While this increases its combat ability significantly it does lead to some problems with it being able to function in tight quarters. Since paladin’s mount can be summoned to you once a day this presents less of a problem than most animal companions. This will allow you to go places it will not fit and have it with you after that, but you are limited in the number of times you can summon it. Also there are a lot of situations where having a lion with you will not be appropriate. Even if the lion is an intelligent celestial being most people are going to view it as a dangerous animal and not want it around.
The divine bond weapon is more than just the ability to get a magic weapon. What makes it powerful is that it can add abilities to an existing weapon. With it a paladin can add 10 different enchantments to an existing magic weapon. If you are fighting trolls, your sword is not flaming and their regeneration is nullified. One of the most useful enchantments to add with divine bond is merciful. This has saves a couple of paladins in my games from falling. Being able to stop a group of innocent people who had been duped into going up against the paladin’s group without killing them was very helpful. It was one of those no win situations where if the paladin did not stop the group a major disaster would have happened and a whole lot of innocent people would have died.
The other thing weapon bond is good for is when the paladin is fighting a lot of weaker opponents. Smite Evil is great vs the BBEG, but is almost useless against a horde of minions. Sure smite evil works great against the lich, but what about his army of undead between him and the paladin. Being able to make the weapon holy to do more damage vs the minions can allow a paladin to deal with them a lot more efficiently.
Either option will work. Normally I would recommend going for the weapon bond as it is usually more powerful in the long run. The fact your GM is allowing a companion that is not normally allowed alters that. You are also in a small party so having an extra combatant will be a big help.
Don’t bother with the item creation feat. As a paladin you have too few feats and skill points to make work well. Since paladins have a limited spell list creating magic weapons is going to be more difficult for you than it would for another character. If someone in the group is going to take item creation feats the cleric would be the best option. They not only have more of the spells needed on their list, they also have access to the entire spell list. The sorcerer only know a limited number of spells, and more than likely those spells are not the ones he needs to create magic weapons.
Keep the lion (especially if it was the GM's initial idea and not yours as a begging, pounce-obsessed munchkin ;-); it'll make you special. --There's nothing wrong with Weapon Bond, but you're basically just duplicating a richer paladin's armory. (E.g., a backup Merciful weapon is only money, etc.)
Magic: ....Dangerously Curious is all you need here, and a few scrolls of Reduce Animal will solve most barrier-to-entry sidekick problems.