You can use Scriban extension as below to fetch random list of children from datasource item.

1. Create the Scriban Extension as below, to generate the random list that take list of items and the number of items to be returned as a parameter.

using Scriban.Runtime;
using Sitecore.Collections;
using Sitecore.Data.Items;
using Sitecore.XA.Foundation.Scriban.Pipelines.GenerateScribanContext;
using System;
using System.Collections.Generic;
using System.Linq;

public class GetRandomItemsFunction : IGenerateScribanContextProcessor
{
  private delegate List<Item> RandomItemDelegate(ChildList item, int randomElementsListSize);
  public void Process(GenerateScribanContextPipelineArgs args)
  {
     var randomItemsDelegate = new RandomItemDelegate(GetRandomItems);
     args.GlobalScriptObject.Import("sc_random_items", (Delegate)randomItemsDelegate);
  }
  public List<Item> GetRandomItems(ChildList items, int randomElementsListSize)
  {
     if (items != null)
     {
        return items.OrderBy(x => Guid.NewGuid()).Take(randomElementsListSize).ToList();
     }
     return null;
   }
}

2. Thereafter, register the above Scriban Extension through below configuration patch:

<?xml version="1.0"?>
<configuration xmlns:patch="http://www.sitecore.net/xmlconfig/" xmlns:set="http://www.sitecore.net/xmlconfig/set/" xmlns:role="http://www.sitecore.net/xmlconfig/role/">
    <sitecore>
       <pipelines>
          <generateScribanContext>
                <processor type="SitecoreCustomExtensions.ScribanExtensions.GetRandomItemsFunction,SitecoreCustomExtensions" resolve="true"/>
          </generateScribanContext>
       </pipelines>
    </sitecore>
</configuration>

3. Finally inside the Scriban call the above Scriban Extension as below, with the datasource children and size i.e 3 as an argument to that extension.

{{randomList = sc_random_items i_datasource.children 3}}
{{if randomList}}
  {{ for i_child_res in randomList  }}
    <p>{{i_child_res.Title.raw}}</p>
  {{ end}}
{{ end}}

Using above changes, you can randomly fetch N number of items from the list.

Hope this helps!!! Let me know in case you face any issues.

You can use Scriban extension as below to fetch random list of children from datasource item.

1. Create the Scriban Extension as below, to generate the random list that take list of items and the number of items to be returned as a parameter.

using Scriban.Runtime;
using Sitecore.Collections;
using Sitecore.Data.Items;
using Sitecore.XA.Foundation.Scriban.Pipelines.GenerateScribanContext;
using System;
using System.Collections.Generic;
using System.Linq;

public class GetRandomItemsFunction : IGenerateScribanContextProcessor
{
  private delegate List<Item> RandomItemDelegate(ChildList item, int randomElementsListSize);
  public void Process(GenerateScribanContextPipelineArgs args)
  {
     var randomItemsDelegate = new RandomItemDelegate(GetRandomItems);
     args.GlobalScriptObject.Import("sc_random_items", (Delegate)randomItemsDelegate);
  }
  public List<Item> GetRandomItems(ChildList items, int randomElementsListSize)
  {
     if (items != null)
     {
        return items.OrderBy(x => Guid.NewGuid()).Take(randomElementsListSize).ToList();
     }
     return null;
   }
}

2. Thereafter, register the above Scriban Extension through below configuration patch:

<?xml version="1.0"?>
<configuration xmlns:patch="http://www.sitecore.net/xmlconfig/" xmlns:set="http://www.sitecore.net/xmlconfig/set/" xmlns:role="http://www.sitecore.net/xmlconfig/role/">
    <sitecore>
       <pipelines>
          <generateScribanContext>
                <processor type="SitecoreCustomExtensions.ScribanExtensions.GetRandomItemsFunction,SitecoreCustomExtensions" resolve="true"/>
          </generateScribanContext>
       </pipelines>
    </sitecore>
</configuration>

3. Finally inside the Scriban, call the above Scriban Extension as below, with the datasource children and size i.e 3 as an argument to that extension.

{{randomList = sc_random_items i_datasource.children 3}}
{{if randomList}}
  {{ for i_child_res in randomList  }}
    <p>{{i_child_res.Title.raw}}</p>
  {{ end}}
{{ end}}

Using above changes, you can randomly fetch N number of items from the list.

Hope this helps!!! Let me know in case you face any issues.