Your concern sounds plausible, at least the thermal printer module I've used it had strong current consumption requirements, but anyway the first analysis you should have done, or at least presented here, is to compare the consumption characteristics present in the datasheet. In advance, what I can suggest is to you add ceramic/polyester capacitors of the highest value possible close to the power of the printer module and make sure that wirings/tracks supports peak current for the worst case, on which all dots of a row are heated at the same time.