Translation:They are getting dressed.
Yes, "get dressed" and "are getting dressed" are specifically used about oneselves, but "dress" and "are dressing" are not limited to oneself, so I believe that "They dress themselves." could be a better alternative than "They dress." although it is a bit emphatic. Still, "They get dressed" or "They are getting dressed" are still the best ways to say it in English.
Not really. In English, reflexive pronouns are only used for emphasis, i.e., there are no common references to "oneself" in most such sentences. Especially, references to self are never made when the action is one that occurs without assistance from another person. For clarity, the British Council says:
We do not use a reflexive pronoun after verbs which describe things people usually do for themselves, such as wash, shave, dress:
- He washed [himself] in cold water.
- He always shaved [himself] before going out in the evening.
- Michael dressed [himself] and got ready for the party.