Most electronics these days support dual 110V/120V and 220V/240V. But, as others mentioned, verify what you are purchasing supports 220V/240V.
You can get two types of adapters (plug style only - not voltage). 1. universal to India-style [Type D] or 2. USA to India-style [Type D]. I would recommend #1. (I've had good experiences with both OREI and Ceptics brands)
The problem that you'll encounter, however, is that electricity goes out sometimes in most parts of India. It's much, much worse in rural areas and NE India, however. I highly recommend a surge protector for the recipients of these gifts.
Unless you are bringing multiple items which are identical (say 3+ tablets, laptops, phones, etc.), you should not have any problems with import duties.
I have traveled multiple times with two video cameras, audio recording devices, my laptop, two phones, a bunch of microphones, and tons of rechargeable batteries (plus the chargers). No problems entering India - leaving with any of this stuff in your carry-on, can be a bit annoying at security sometimes.
Word of warning! I went to India in August (2017) and my LG G3 battery died. There was literally no place which sold these, except some Amazon.in places which all had 1 star ratings. My phone was unusable the entire month I was there. Be warned that if you get a brand that is not serviceable or have replaceable parts in India, any damage will likely cause it to be an expensive paperweight. You might want to seriously consider bringing smaller gifts and offering to buy these electronics while in India to avoid basically all the issues/concerns that you have.