I will be going during 1st week of april. Will it be very cold at jiuzhaigou & chengdu?

What will be their average temperature at both JZG & chengdu day & night during 1st week of april. Will there be a great difference? Is the scenery good for phototaking? Il be going with my parents. I heard that its not very ideal for people with high blood pressure to travel because of its altitude. Does the people with high blood pressure need any special medication? As we will be staying there for 2 nights. Thanks