How can I default a radio button to be on?

Hi,

Our "fundraising" is very specific.
We're asking someone to "back" our project with specific amount of money. Simplicity is key, so we'd like to force the radio button for the "crowdfunding goal" to be on.

I tried changing this line of code:

<div class="wdf_reward_choice"><input type="radio" checked="checked" name="wdf_reward" value="'.$index.'" '.$disabled_input.'/><span class="wdf_level_amount" rel="'.$data['amount'].'"> '.$wdf->format_currency('',$data['amount']).$limit_text.'</span></div>

in lib/template-functions.php, line 644
By adding checked="checked"

When I reloaded the page the button was indeed already "checked", but it still required me to click it! Is there some javascript or AJAX that is tracking the click that also needs to be changed?

I know this request is "special" and beyond normal - so, can I pay your team extra to either add this feature or tell me how I can add it to my version of the code?

Ultimately, we want to hide the raidio button all together, but I can do that CSS, so that the design is VERY simple and clean, much like this site:
Example of clean design: https://www.weargustin.com/store/1107