Hi Elena!
My family stayed at Old Key West last year and had a great time exploring the Resort. We all agreed that we could spend a week at that resort with everything it offers, never even go to the Theme Parks, and never get bored! My kids were the most excited about the playground, arcade and pool that Old Key West offers.
Even though your rooms might not be ready, Disney Resorts are great about letting you check in and then calling or texting you when your room is ready. They will also hold all of your bags so that you can start your vacation.
Your Resort offers a couple of places to eat, Olivia's Cafe & Good's Food to Go are available pretty much all day. You could also get on the ferry boat that takes you to Downtown Disney where shopping and dining are amazing.
Of course, if your Park Hopper tickets include your arrival day you can get your group onto a Disney Bus and head to the Parks! My family likes to start at The Magic Kingdom for our first Park because seeing Cinderella's Castle and riding the classic Disney rides makes all of us happy!
I hope that you have a fabulous time this July!