I need some development effort for my shopify store. I want to sell City Tours & Attraction Tickets. When creating price we need to have variant for Adult Price & Child Price and let user select a date from calender. [No date range. only one date]. If date is on Saturday & Sunday, Automatically the Sur-Charge Checkbox will be checked. The price should appear on shopping cart. If you know how to install Bookthatapp will be best.