I agree, it sounds like you know the answer. You have the opportunity to give a home to a couple of dogs that truly need it. What you are doing for them in no way detracts from what you have given to Charlie in time, attention and love. If this will help you to deal with her loss, then it is a good thing. It shows, IMO, great maturity and forethought on your part that you are preparing for the grief you will feel when it is time to say goodbye to her. If anything it is a tribute to how much she means to you that you would need the comfort and distraction of a new dog to help you through your loss.
That's for you.
That's for Charlie.

