If you want a real mess, come see my mud/laundry room in fall. You can barely move for things I'm bringing in.
Yes, all those individual green things are petunia plants. You'll have loads. Despite the small seed size, I've always found them easy to grow. Leave them as is for a while longer until the seedlings are a bit larger and easier to handle. Hold by the leaves only when you transplant into cells (which I find easier and less bulky).
The geraniums may not bloom this year as they're a slower grower. Bring them inside for winter and you'll definitely have flowers next year. Normally I start geranium seeds in Nov/Dec.