Karlie here from the Shopify Guru Team! I've gone through your storefront to see if I could run an order through with a credit card from your PayPal Express. The option for your customers to checkout as a guest and pay with their credit card without having to enter PayPal login details is available in your checkout on your website. If you're not seeing this option then you may just need to clear your cookies and cache for your browser. Make sure you browser is up to date as well and that should resolve the issue for you!
I hope this helps, but if you have any further questions - be sure to ask and I would be happy to help!
You're so welcome!
If you're not seeing that option via mobile - I would recommend contacting PayPal support. They may be able to tell you more about how to use that feature on a mobile device or dig into the problem for you.