I do this all the time. One thing I've noticed when ordering online now, is that the site reminds you that you have rewards, and do you want to use them- it was awesome- I had $40! Also, I shop way more at Old Navy than the Gap, but my CC is a Gap one...
It's awesome...it's like four cc in one. You will earn reward points that you can use at any of them. Plus...you can use the cc at the outlets.
Happy spending!