Is my team good enough to face the Elite 4?

You definently need to edit your pokemons' moves, but the creatures you have should do fine once that is done. Here is an easy way to defeat the Elite Four with the pokemon you currently have.

Teach your groudon flamethrower over fire blast and thunderbolt over rock smash (don't teach weak HM moves to your strongest pokemon) and teach your salamence fly over headbutt.

Put groudon in the front of your party and defeat the league in the manner shown below, switching to salamence whenever neccessary.

Sydney:
Absol-Use slash/dragonbreath or dragon claw
Cacturne-Use flamethrower/flamethrower or fly
Mighteyana-Use slash/dragonbreath or dragonclaw
Sharpedo-Use thunderbolt/dragonbreath
Shiftry-Use flamethrower/flamethrower or fly

Pheobe:
Banette-Use earthquake/dragonbreath, dragon claw or
fly
Banette-Use earthquake/dragonbreath, dragon claw
or fly
Dusclops-Use earthquake/dragonbreath, dragon claw
or fly
Dusclops-Use earthquake/dragonbreath, dragon claw
or fly
Sableye-Use earthquake/dragonbreath, dragon claw
or fly

Glacia:
Glailie-Use flamethrower/flamethrower
Glailie-Use flamethrower/flamethrower
Sealo-Use thunderbolt/dragon claw or fly
Sealo-Use thunderbolt/dragon claw or fly
Walrein-Use thunderbolt/dragon claw or fly

Drake:
Altaria-Use thunderbolt or slash/dragonbreath or dragon claw
Flygon-Use slash/dragonbreath or dragon claw
Flygon-Use slash/dragonbreath or dragon claw
Salamence-Use thunderbolt or slash/dragonbreath or dragon claw
Shelgon-Use earthquake or slash/dragonbreath or dragon claw

Steven:
Aggron-Use flamethrower or earthquake/flamethrower
Armaldo-Use flamethrower or earthquake/flamethrower or fly
Claydol-Use flamethrower or slash/fly or dragon claw
Cradily-Use flamethrower or slash/flamethrower or fly
Metagross-Use flamethrower or earthquake/flamethrower
Skarmory-Use flamethrower or thunderbolt/flamethrower

When choosing which move to use, use the one which has either the most pp at that moment or, even more wisely, which one should have the most pp left over.

Also, you may have noticed that there are some cases where a move is mentioned more often than it can be used with its natural pp.

This means that you will have to choose to use said move on less pokemon than it is mentioned with, so use some thought when picking whether or not to use it on any given creature (note that this problem can be bypassed with temporary/permanent pp raisers, but this is not at all neccesary and often a bad decision).

You definently need to edit your pokemons' moves, but the creatures you have should do fine once that is done.

Here is an easy way to defeat the Elite Four with the pokemon you currently have.

Teach your groudon flamethrower over fire blast and thunderbolt over rock smash (don't teach weak HM moves to your strongest pokemon) and teach your salamence fly over headbutt.

Put groudon in the front of your party and defeat the league in the manner shown below, switching to salamence whenever neccessary.
Sydney:
Absol-Use slash/dragonbreath or dragon claw
Cacturne-Use flamethrower/flamethrower or fly
Mighteyana-Use slash/dragonbreath or dragonclaw
Sharpedo-Use thunderbolt/dragonbreath
Shiftry-Use flamethrower/flamethrower or fly

Pheobe:
Banette-Use earthquake/dragonbreath, dragon claw or
fly
Banette-Use earthquake/dragonbreath, dragon claw
or fly
Dusclops-Use earthquake/dragonbreath, dragon claw
or fly
Dusclops-Use earthquake/dragonbreath, dragon claw
or fly
Sableye-Use earthquake/dragonbreath, dragon claw
or fly

Glacia:
Glailie-Use flamethrower/flamethrower
Glailie-Use flamethrower/flamethrower
Sealo-Use thunderbolt/dragon claw or fly
Sealo-Use thunderbolt/dragon claw or fly
Walrein-Use thunderbolt/dragon claw or fly

Drake:
Altaria-Use thunderbolt or slash/dragonbreath or dragon claw
Flygon-Use slash/dragonbreath or dragon claw
Flygon-Use slash/dragonbreath or dragon claw
Salamence-Use thunderbolt or slash/dragonbreath or dragon claw
Shelgon-Use earthquake or slash/dragonbreath or dragon claw

Steven:
Aggron-Use flamethrower or earthquake/flamethrower
Armaldo-Use flamethrower or earthquake/flamethrower or fly
Claydol-Use flamethrower or slash/fly or dragon claw
Cradily-Use flamethrower or slash/flamethrower or fly
Metagross-Use flamethrower or earthquake/flamethrower
Skarmory-Use flamethrower or thunderbolt/flamethrower

When choosing which move to use, use the one which has either the most pp at that moment or, even more wisely, which one should have the most pp left over.

Also, you may have noticed that there are some cases where a move is mentioned more often than it can be used with its natural pp. This means that you will have to choose to use said move on less pokemon than it is mentioned with.

So use some thought when picking whether or not to use it on any given creature, (note that this problem can be bypassed with temporary/permanent pp raisers, but this is not at all neccesary and often a bad decision).

Maybe you should teach them more effected moves that are closer to the nature of the specific Pokemon.