I've been asked to make 250 mini cupcakes and 100 cakepops. It will be simple designs. Buttercream frosting for cupcakes. I've never made this amount for anyone before. They are also willing to pay for delivery which is within my city. How much should I charge for everything?

Since  you apparently have sold some before what kind of pricing did you use?  Mini cuppies probably should run about $2 ea and pops near that.   It all depends on sooooo much such as your location, how much you have invested in ingredients, packaging, and so very much more.

And make sure you get $$$ up front....... as we have all received those "happy Wedding" inquiries for large orders, money orders and excess handling fees.