how to change minimum widget size of iframe to 1024px

Site URL: https://www.acrossthecreekcabins.com/book-a-cabin

Im trying to embed the little hotelier booking engine into a code block on one of the pages of my website but I have the issue where it reverts to the mobile version for the desktop and causes the embed to "grow" on the page. I need to know how to create the minimum width of the iframe to be 1024px.

Here is the coding I have been using to embed the booking engine:

<div class="ibe" data-region="emea" data-channelcode="acrossthecreekdirect" data-widget="embed"></div>

<script src="https://widget.siteminder.com/ibe.min.js"></script>

The link to the page I am working on is here: www.acrossthecreekcabins.com/book-a-cabin

Add to Design > Custom CSS

/* Book a cabin iframe */
iframe#iFrameResizer0 {
    width: 100% !important;
    max-width: unset !important;
    min-height: 700px !important;
}