We have sort of the same problem - a too small, but full house that we won't be moving from for a year or more. We didn't register for much, but what we did was register for a few things online at myregistry.com so you aren't limited to a single store. We picked out a few replacement items (teakettle, towels and washcloths, sheets, baking pans, etc.) and then a few items we still need that won't take up too much room (like a small steam cleaner, BBQ grill utensils, universal remote...). Also, remind your FI that he can add things like video game accessories, tools, camping gear, whatever he's into which might get him a little bit excited about it too. We also put some Home Depot gift cards on there to put toward a new lawn mower.
Try not to stress about it and have a good time!