Blushy

Hi i have a florist, not overly large scale yet, but i would like to offer more products to purchase, mainly for valentines day coming up I will be uploading specific bouquets to purchase, id like to offer add-on items such as chocolates, cards, & other giftables however i dont want these other items to be purchased simply on their own as I dont want customers to only purchase a £10 box of chocolates for delivery, as we have a minimum spend of £40 in order to qualify for delivery.... in saying that, is there a way they can purchase other items as long as they spend over £40? but back to my question - how can i create an add-on part to the item page once they select the bouquet? or can it be offered in the checkout page? 

i hope my question wasnt too confusing. 

many thanks.