I think that is fine.... but you also might want to have one somewhere in the house.
I know when I had Riley in his x-pen... I also had one in the corner of my place....and that one is still there. He really would not use the one in his x-pen and even in the middle of the night he would Whine and I would get up and take him to the one in the other part of the house......
When he got a little bigger, he would Whine and I would just lean over and unbolt the xpen and he would run to the other one, do his business and then run back into the x-pen where I would lean over and bolt him back in.
That is how I trained him to use the pads First.... He will now use the pads, if he has to when I'm not home, but he will also go outside.
Hope this helps!