We postponed our wedding - gift ettiquette?

So due to a lot of stuff going on - mainly losing my dad two months before my wedding and my brother being at boot camp and some family drama on my FH's side we decided to postpone our wedding until after the holidays. My dad's parents were still really raw at losing their son to Alzheimer's and the timing didn't feel right. We made this call 2 weeks before the wedding date we had originally picked (Oct 4) and notified all the people who had RSVPd, especially out of state. Covered cancellation costs and such.

I just changed our date to our tentative one in January on our Target registry yesterday (Oct 5) when we received a package from Target on our doorstep. I'm guessing it's from someone who couldn't make it and had ordered before we postponed. We also received a gift from a neighbor early. I don't know who bought us a gift from Target and we haven't opened it yet.

Should I open it now so I can find out who it's from and send a thank you note/explain things? I don't have to return it do I? We are still getting married...just later. If it's from someone who can't make it I'd feel bad if they didn't get a thank you note until February for a wedding that was supposed to be in October but I don't know the ettiquette on that.