golden beginning heat cycle

Question
Our 7 month golden is in heat, we saw the first spotting yesterday and have noticed the swelling.  We have a fixed 5 year old male and a non fixed 3 year old male (my brother's dog that is staying with us).  How long shall I confine our female?  We intend to haver her spayed after this first cycle for sure!  Thank you for any advice you can give.

Answer
Keep her away from all males including the fixed one until 3 weeks after she started the discharge.  Some neutered males will still mate with a female, and maybe injure or infect her.  Don't underestimate what her and the male will do to get together.  Be prepared for her to make desperate attempts to get loose.  Put nothing past her.  Once loose, no end of bad things can happen.  

In three weeks, you will have no doubt about going ahead a spaying her.  Thank you for planning to do so.