So you're offering 2 of your invites for 10$ a month each, yet the whole subscription costs 35$. Sounds like a good deal for you.
Edit: If the offer is 10$ a month for both, it's a good deal for everyone.
Price seems fair. With Showtime it's $45 plus tax. OP have you tested how many streams work at once?
not sure but i can tell you what my family does
we created another "shared" gmail account, we use that for the youtube tv (chrome cast ultra, tablets and mobile) we are an family of 6 in a single home and had no problems and streamed about 7 at a time on an single user without problems.
not sure they have a cut off, but i maxed out @ 7 and everything was fine.
NOTE: this service works so well with us that we have cancelled our TV service and upgraded our internet