Surprise allows a Standard Action...
Readying is a standard action...
You can make a Partial Charge if you are limited to only a standard action...
From the SRD Wrote: In initiative order (highest to lowest), combatants who started the battle aware of their opponents each take a standard action during the surprise round. You can also take free actions during the surprise round. If no one or everyone is surprised, no surprise round occurs.
Readying is a standard action...
From the SRD Wrote:Ready
The ready action lets you prepare to take an action later, after your turn is over but before your next one has begun. Readying is a standard action. It does not provoke an attack of opportunity (though the action that you ready might do so).
You can make a Partial Charge if you are limited to only a standard action...
From the SRD Wrote:If you are able to take only a standard action or a move action on your turn, you can still charge, but you are only allowed to move up to your speed (instead of up to double your speed). You can’t use this option unless you are restricted to taking only a standard action or move action on your turn.