Timeline Mistake

I'd probably try to contact the hotel and see what can be done. If I were a guest traveling for a 3 pm wedding and needing to stay in a hotel, I'd definitely want to check into the hotel by 1:30 pm at the latest in order to shower, freshen up, get dressed, get to the venue, etc. Otherwise, I think you'd have a lot of out of town guests showing up late to your ceremony. I don't think people would show up to your ceremony dressed with their luggage, then go to the hotel to check in, and then go back to cocktail hour...I'd either see if the hotel can make an exception for your guests, or push back your start time and send an email clarifying that you had the wrong time on the invitations

This isn't a huge deal. They'll either go to the hotel beforehand and check in if they can, or check in and leave their bags at the desk, or they'll do it after the wedding. You're overthinking this I think.

We had a ton of weddings we attending last fall out of state and every hotel allowed us to check-in early. One hotel only allowed an hour early (it was a holiday weekend and busy), but all the rest let us do up to 2 hours early. We basically just said our flight landed early and we were part of the wedding party that evening and there were no questions asked! Most hotels try to accommodate their guests as best they can so I don't think this should be too much of an issue for your guests!