Hi Thejesh,
For this kind of application, the commonly used supply voltage for this type of amplifier is +/-5V. This is to take advantage of the larger input voltage range. Take note that there is a voltage known as a half cell potential develops across the electrodes that appears as a dc offset in ECGs, EMGs and EEGs applications. This dc offset actually limits the amount of gain that you can apply to the amplifiers and should be considered if there is a need to increase the your supply voltage. Some designers also often use +/- 7.5 V to handle severe environment such as in operation room wherein there will be a lot of interfering signal present.
I think it would be safe to use the +/- 5 V supply voltage for your circuit.
Other options that you want to consider for future design which I think is very suitable for this type of applications is to use the AD8237. This is a micropower instrumentation amplifier which is an excellent choice for battery operated /portable system applications. This can be implemented on in ECG applications using a 5 V single supply voltage (because of its unique architecture that can amplify signals with common mode voltage at or even slightly beyond its supplies ). Although this will cost you to use extra components to compensate for the half cell potentials of the electrodes. You can see the sample circuit design on figure 77 of its datasheet.
Let me know if you need anything else.
Best regards,
Emman