Hey @David,
While we cannot offer help with code customizing and such, I think a helpful bit of advice here would be to use the do_shortcode() function in WordPress instead.
You can learn more about that function here → https://developer.wordpress.org/reference/functions/do_shortcode/
This would let you use all shortcode arguments/options as normal, and so you could use something like this instead of what you posted:
if ( function_exists( 'do_shortcode' ) ) {
echo do_shortcode( '[tribe_mini_calendar category="party"]' );
}
You’ll have to take the reins from here on further tweaking and developing, but I hope this helps! And be sure to check out this guide to our widget shortcodes if you have questions about those → https://theeventscalendar.com/knowledgebase/pro-widget-shortcodes/
— George