True, but you can do that with no expensive extras on an Arduino.If this device will spend any significant proportion of it's time awake a micro-controller is a better bet than a Pi for power consumption.
It would help to now more about the application.
1. How much active playing time is required?
2. Does response time matter? Is it OK to rely on the wakeup timer + boot time + mp3 file load to get to start of the sound?
3. Is the playback purely periodic, or should it play at specific times of day?
4. Is battery management required (battery level warning, charge control etc)?
5. What UI is required? Touch screen is mentioned, but no clue as to what user interaction is required. A few buttons and text LCD can achieve a lot.Obvious function are select sounds / times to play, which might be easilly done using a simple text menu.
6. Would connection to another device be appropriate? E.g. configure via Bluetooth from a mobile/tablet?