Hey! Nice. There's an open API for XUMM. You can send Sign requests to the API. You'll get an URL / QR / ... back to show to the user. Your frontend can subscribe to status updates, your backend can receive hooks.

Exactly that (not wanting the user to enter details in your environment) is what the XUMM API & flow for the end user will realize. You can use a numeric destination tag for each payment to match it, or even an Invoice ID or Memo (free text). Or even something completely off ledger, as each request will have a XUMM payload ID, and the callbacks from the XUMM platform will contain both the original XUMM payload ID and on ledger transaction hash. You can even send off ledger meta data with a sign request in the custom_meta object: https://xumm.readme.io/reference/post-payload

Once a user accepts your payment request, you'll get a user specific token so you can even send push requests the next time.

You can request XRP or an IOU (eg Bitstamp USD / Gatehub EUR) and if the end user pays you in another asset the XRPL decentralized exchange will convert: you'll always receive what you requested.

Dev Docs: http://xumm.readme.io

Dev Console: https://apps.xumm.dev

Happy to assist if you need help :)