I need a Wix velo expert to help extend the functionality of Wix Stores

The website is nomnomnosh.uk. initially the service was collection only, then itr became collection from two locations. In the absence of any click and collect functionality this is currently worked around with a lightbox message on entering the shop and a custom field during checkout to specify the location. We now want to add a delivery option via a local ecoCycle enterprise (ie delivering by bike in the local area). Our idea is to have a fulfilment product which can be selected during ordering to indicate the chosen collection/delivery option (all zero cost). We then need to be able to identify when a ecoCycle delivery product has been added at checkout and on completion of payment pop up a new page linked to the ecoCycle delivery provider who will then take the booking (and payment for the delivery service). There is more in terms of communication but the Velo part concerns identifying when the product is in the basket and triggering the link after payment. We are looking to develop an ongoing relationship with an experienced Velo coder. I have coding experience from way back in C and Fortran (!) and still code VBA, but I don't have the time to learn Javascript of Velo or maintain this knowledge. Viewing the website should allow one to easily understand the nature of this plant based food business. I've selected Javascript as the skill because there is no option for Velo (!) but I'm aware they are forms of the same...