Well done to your parents for letting you be in charge! We better make them good then.
Two questions I forgot to ask; Are they wire baskets and what size?
I will presume for now they are and they are 12/14".
The reason I asked about length is there are two long trailing plants that really catch your eye in hanging baskets. Seeing as they are going to be in full sun you could use nepeta. It will trail to the ground and as the baskets are only 5ft high you may need to nip the bottoms off. They are a greeny grey colour with white margins. No flowers but that is what gives the basket the full, luscious, look.
Plant 3 of those in the sides slightly lower than the middle. Above them you could use trailing verbena. Come in bright red, blue, purple and white (I think there is also a purple and white stripy flowered one) and give you volume and trail. Plant 3 of these higher up on the side and between the nepeta. This should cover all of the sides of the basket. Mix the colours if you want.
In the top you could use trailing petunias. They come in all colours so lots of choice. Again use three or use two and an upright like a geranium at the back.
That should look pretty good. Make sure you add lots of feed in the basket. It will have to sustain a lot of plants right through the summer and "swell gel" added near the bottom in a little handful will save on some of the watering.
Hope they look fantastic!!