If I ion cannon someone before their shooting turn, can they still attack?

Yes. Ion weapons just deal an ion token.

Smalk shios are ioned after one token and large ships after 2.

Ioned ships don't choose a maneuver and moves 1 white straight, but is otverwise unafected

Yes. Ion weapons just deal an ion token.

Smalk shios are ioned after one token and large ships after 2.

Ioned ships don't choose a maneuver and moves 1 white straight, but is otverwise unafected

This^

So an ioned ship can still use actions like boost and barrel roll to provide a small degree of control, and ioning a ship does not prevent them from firing.

After executing the 1 manoeuvre remove the ION Symbol and then perform actions and combat as normal. Page 3 of he FAQ/ERRATA