Thank you so much for your post, and welcome to the forums.
Whilst you will be able to put your Netflix log in details on to both of your TiVo® boxes, and a number of other devices, you may find that you'll be limited on how many devices you can have on at the same time.
If you pop along to https://www.netflix.com/gb/ (as long as you are not logged into your Netflix account on the computer you're using) and scroll to the bottom of the page and you'll see the following
"Choose one plan and watch everything on Netflix."
Under this heading you'll see the different price plans that Netflix offer, the basic account will offer you just 1 screen at a time. Meaning if you want to watch something on one TiVo, you'll need to come out of it before going into it on another.