Our special education classes do a valentine's fundraiser, "Cookie grams". They are $1 and they say they go over really well. So much that they continue to do it. I don't know how they get the cookies if the parents bake them or they buy them in bulk but either way would work.
I've seen the valentine delivered to classes go over well, but that was in high school and college. A candy bouquet isn't expensive to make, but needs volunteers to make.
Instructions for candy flowers:
Kiss rosebuds-
Pierce a Hersheys kiss with an bamboo stick. Wrap the kiss in a small piece of colored celophane.
Wrap the bottom of the of the celophane and the bamboo stick with floral tape.
I think you can do it with hard candies and suckers too.
Another little treat to make if you can market it is to wrap Hersheys mini bars with personalized wrappers. Several clever sayings is all you need. It's very easy.
Delivering balloons was cool. I don't have any idea how much money could be made with these ideas, but they are fun.
The PTA doesn't do Valentines fundraisers, our student council does...but they do candy grams, and carnations. I believe each costs $1.00. Not a huge fundraiser, but fun for the kids.