All coin flips are completely independent. Regardless of how many you intend to flip and and how many you have flipped already and there results, each coin flip will have a 1/2 chance of being heads or tails. This deals with the law of large numbers. We can't apply the law of large numbers to a scenario in which there are only 2 trials. The greater the amount of trials preformed, the lower and lower the standard deviation becomes. When tossing coins, no matter what, chances are 50-50.
Knowing that you're tossing two coins does not change that.