I can not tell if you can put two of these modules in parallel without seeing a circuit diagram.
However if one module can deliver enough current for your application, you can do it with only one module.
LiPo cells are a bit picky when it comes to voltages above 4.2V. When you put two cells in serie the maximum charching voltage would be 8.4V. Now consider one of these cells is defective and ceases to charge at 3V, the other cell will now get 5.4V - too much. Thats the reason why in a serial configuration each cell needs it's own charging or balancing circuit.
The key here is that you like to put the two cells in parallel, they will be charged up to 4.2V, no problem. They will not catch fire or explode because of over voltage.
As usual there are drawbacks, in this case two.
- The charging current will be split, the charging time doubles.
- If one cell is defective it can discharge or even demage the second one, they are not isolated from each other.
As a sidemark, before putting them in parallel I would bring them to the same state, e.g. fully charge them separately.