I don't think visitors can level hills, so that part, you'll have to do yourself. And I think only best friends can use axes and shovels, so you'll have to add people specifically and give them best friend privileges for them to help you. But by that point, it might be easier for you to do it yourself as you're leveling everything. I'm not sure, but the cleanup feature of the terraforming tool might get rid of flowers for you, so you can try that, too.
