If you want to use the Lazy River at Cabana Bay, you will need to bring your own tubes or buy them on-site at the resort. I don't remember the exact cost, but it was around $10 - $12 per tube. Much cheaper to bring your own. They will inflate any tubes for you at the little shack, so no need to try to pre-inflate it.
I would definitely leave some time to "play" at the resort. It's a great place with plenty to do.
As for the parks, We went in July last year and as long as you take advantage of the Early Morning hours, you will be fine. We didn't have Express Pass and got on everything we wanted. Minions is best to do right at Morning Hours opening or it will get over an hour very quickly. We did it on the way back to Gringot's and got on in 10 minutes. Then once you do the HP rides once going through the Queue, we just started to do the Single Rider lines. You miss some of the queue, but get on in 10 minutes vs. 60 minutes. No brainer for us.