[EpicInterlock]

Polymeric sand is generally used for gaps between pavers. I'd go with polymeric sand, but please read and follow the directions carefully!

As for the 1" gap, it's completely up to you, but if you're not used to using a concrete cut off saw to cut small pieces of pavers, then I'd use the polymeric sand. (Another thought about using small pieces - if you don't have extra old pavers, using new pavers might not be a good idea because your existing pavers have been weathered so it won't be exactly the same colour as the newer ones.) After you follow the directions, the polymeric sand will basically turn very concrete hard, which should be sufficient for a 1" gap.

Good luck