Brocholi and Bacon Salad

I got this recipe from my SIL courtney.
1 head broccoli, chop up
1 head cauliflower, chop up
1/2 c red onion, chop up finely
1 c cheese shredded
1 c sunflower seeds
1 pkg bacon cook

Dressing:
1 c mayo
1/2 c sugar
1/4 c vinegar