Easy Recurring Shopify App at Checkout or Elsewhere

[Dgoldfe13]

My Shopify is a small business and we don't collect subscriptions or recurring payments regularly. I need to collect recurring payments for only 1 product page with 3 different variations that are eligible for "subscription" recurring charges. There are two options that are non-recurring charges, but I can remove those if necessary to get the job done. 

Recurring Charges

Mondays | 9:00 - 9:40 | Ages 2-3 | $60

Mondays | 9:50 - 10:30 | Ages 3-4 | $60

Mondays | 10:40 - 11:20 | Ages 5-6 | $60

Non-Recurring Charges (One-time)

--- Add Jersey (extra one-time cost) | $25

--- Add a Soccer Ball (size 4) | $15

Here is the page: https://gophoenixsports.com/products/goddard-school-enrichment

Ideally, I would like the customer journey to look like this:

Visit page (see above)

Select class drop-down > Mondays | 9:00 - 9:40 | Ages 2-3 | $60

Select Camp Option > None apply

Select Add One-Child > input info

Add to Cart > Checkout

Clearly stated "recurring monthly charge" preselected can't change

Or

Below "add to cart" > 

Clearly stated "recurring monthly charge" preselected can't change

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I want a simple and easy way to do this. Our Shopify is heavily customized to add children info and I am not sure that can place this without much customized coding into the "product information" section on the product theme. 

I can set up a notice at states this would be a recurring payment on the "product page" but I need a section at checkout or somewhere that would be a preselected checkbox (unchangeable) for "recurring monthly charge".