My take on this - if you're pretty close to them and if you really do KNOW they want to be invited, then invite them. no harm there. It's when you get to more distant relatives/friends where you think "oh, but what if they hear I had a shower?" that I don't necessarily feel you should invite them. Reality is- MOST people who live OOT don't expect to be invited to showers. Showers are NOT the same as weddings and many people aren't going to travel for them and will actually feel like they are being invited "for the gift". Simply put- showers are NOT "invite all" events. Doesn't mean don't invite OOT people. But exercise caution and realize that it's an event on the same level as a birthday party. Not a wedding.
All of this. When I put together my guest list I thought about friends and family that might be butthurt if they heard I had a shower and weren't invited so I put them on the list.
Like PP said, you know your family best and that should help in deciding who to invite.