Speakers: danger of blowing things up
Since the module you are referring to is this one as far as I can tell as it is the only one they make.
https://cdn.shopify.com/s/files/1/0029/5387/1430/files/MP3-Sound-Chip-Module-User-Guide.pdf?v=1592836934
As long as you connect your two 4 Ohm speakers in series it is perfectly safe. In parallel it is hard to tell since there are no specs on the module beyond what I have provided.
In series two 4 Ohm speakers will provide the same impedance as one 8 ohm speaker. So it will be completely safe, the wattage rating is only the max the speaker can handle, it doesn't indicate what it will pull, that is determined by its resistance and the drivers voltage (which in this case doesnt change.