The proper way of testing is with the wheel on. You cannot test with the wheel off because the only thing holding the rotor is the small allen bolt. This could explain the small play that you felt. What you do is:
1. Jack up one side of the car
2. Grab the wheel horizontally and try moving it side to side (this is to test tie rods there shouldn't be any play if there is you need to change tie rods or drag link).
3. Grab the wheel vertically and move up and down. This is to test wheel bearing. If you have slight play you need to retorque the wheel bearing).
4. Repeat procedure on other side. Make sure to do one at a time. In other words one wheel has to be on the ground.
Checking ball joints requires some kind of bar and it gets a little more complicated because there is tension from spring. Better leave that for your mechanic. He can check it in about five minutes.
However, I am still leaning toward the upper ball joint. It's very simple to check. Have your mechanic disconnect the upper control arm and check the ball joint by moving it around. If it's dry, have it replaced. Your mechanic probably won't have the patience of trying to grease it up, since it's a sealed unit.
I think it's pretty safe to travel with the car. Just get it checked as soon as you get back.