You need local currency that is the only legal tender in Indonesia. As for must do....we know absolutely nothing about you, nor what you expect from your trip to Bali. It is impossible to offer advice. Surely you knew what you intended to do when you chose Nusa Dua & Seminyak for your stay?
Please do some research, start with the things to do tab, top of the page.
Ya, should have elaborated on the likes. Shopping, any historical monuments, local flavor on Balinese culture, good places to eat, clean beaches for relaxation, any local must see places (read rice terraces somewhere).
Not interested in night life.
You're staying in the wrong areas for culture, rice terraces etc, so will need to arrange a driver, agree upon an itinerary and a price, and be prepared to spend quite a long time sitting in a car.
Bali beaches are not the best, but you are staying at two beach areas, so hopefully will enjoy them.Edited: 08 June 2018, 10:43
Suggest you give the exact Hotels you've booked. Especially important for Nusa Dua.
Nusa Dua is just a manufactured resort area. Mostly 5* AI/Convention centre style hotels, often gated, often little to nothing outside except a service road and another hotel.
Your exact hotel will determine if there are any 'local" places to eat (I don't count having to get a taxi somewhere as 'local').
One persons 'must see" is anothers "why bother". You need to read up on Bali and see what interests you personally.
But where you are staying will involve a driver.
A private driver for the day costs IDR600k. That is for the whole van privately to yourself NOT per person. No extra charges. 9am to 6/7pm.
Do/see what you want, stop where you want, have lunch when and where you want.
Most sights you do not need a guide and entrance fees are IDR50k or less or free.
A said above only local currency. Change your US$ at an authorized Money Changer only.
Don't bring INR you'll get a very bad exchange rate
For culture, rice terraces etc, you would be best to spend some of your time in Ubud. I think that only a day trip to that area would be a waste of time.
It would be best to re-consider staying in Nusa Dua for the reason NotaPigsty mentioned. The area mainly caters for large tour groups and seminars and is probably the most expensive district on the island. Seminyak would be fine but you could also consider Sanur as an alternative and it’s generally cheaper.