I love Blizzard Beach, but be warned that it gets verrrrrrrrry crowded in the summer. With July 5th being a holiday for most folks I wouldn't be surprised if there are near record crowds if the weather is nice. My advice is to get there very early (at least 30 minutes before opening) and to have your admission purchased in advance. After entering you'll want to quickly grab chairs and ride any of the bigger slides that your family really wants to hit. Lines will probably be prohibitive from around 11-2 so this is a good time to enjoy the theming, wave pool, lazy river, etc. where crowds will be less of an issue.
A second piece of advice is that if an afternoon storm hits, try to ride it out. We were there once when it rained off an on all afternoon. People left in droves. Slides did close initially when there was lightening, but re-opened and stayed open the rest of the afternoon. We practically had the place to ourselves. It was plenty warm and we were already wet. One of my family's favorite Disney memories.