I'm a retired realtor in Westcester County. Before you start renovations, the key question is how long do you plan to live in this home. If the answer is 5+ years, go ahead since you will enjoy the finished product of the renovations. If you plan to sell within 5 yrs., get several realtors opinions as to the current market - how much more will your home sell for with the added renovations; how long does similar homes stay on the market before selling.
Another concern is home inspections. Buyers will renegotiate and reduce their offer if a home inspections shows repairs are needed for plumbing, electrical, roof, structural, mold, heating/cooling system, etc. If you are not 100% positive that your home will pass the inspection test with flying colors, spend the money to fix these issues first - before undergoing any renovations. It will be far cheaper for you to fix any issues than a buyer reducing their offer by $10,000. or more.
Finally, is your kitchen and bathrooms modern looking or was the last time you did renovations back in 1980? If your kitchen and bathrooms don't look like 2015, spend money on this instead of adding a bedroom. Buyers look and reject homes based on the kitchen and bathrooms. As for an extra bedroom, buyers are well aware of putting in bunk beds or twin beds to sacrifice an extra bedroom. The master bathroom is an added plus but not sure if you will get 100% of your investment back.