I highly recommend making an appointment with your local Social Security office. Both of you go in. That way you can find out about *all* the options available to you. I wish we had done it sooner. We didn't have to make any decisions that day, but we left with a much better understanding of the advantages and disadvantages of retiring at specific ages.
You mentioned age 70. I had thought we would both wait until 70 to start drawing SS but, once we saw how long it would take us to break even with retiring at our earliest age, it didn't make sense for us to do that. There are so many variations depending on number of quarters worked, income during those quarters, etc. that it really is important to make an appointment with SS so you understand all of the options that apply to your particular situation.
Incidentally, if you are actual retirement age and decide to take SS, you are not penalized even if you work full-time. My dh works full-time and still gets his full SS benefit. (The SS benefit is taxable as income.) In our case, retirement age was 65. It depends on the year you were born, though, so again it makes sense to sit down at the SS office and find out exactly what your situation is.
My biggest wish is that we lived in a paid-for house. I think that makes living on retirement income easier. It's also a good idea to develop some extra sources of income. Examples would be moving to a house that has an apartment or lower level you can rent out, developing an eBay or Etsy store, etc. My dh has met retired men in their 80's who are drivers part-time for a local car dealership. We have also seen retired business workers working at Fleet Farm.
Basically you have to figure out all your expenses and balance that against the income you will have. You need a comfortable excess of income over expenses to survive inflation over time.