Playa field total_children tag doesn't work inside a conditional statement

Edit Subject

I've got 2 different related content fields which I want to show in an ASIDE. I only want the aside tag to be printed if there is content in either of these fields so I check for it first. But this doesn't work:

{if ("{pf_event_related_event:total_children show_expired="no"}" >= "1") || ("{pf_event_related_content:total_children show_expired="no"}" >= "1")}

<aside>

	{if "{pf_event_related_event:total_children show_expired="no"}" >= "1"} 

			 <h2>Related events</h2>  

			{pf_event_related_event 

			status="{gs_status_default}"

			orderby="date" 

			sort="desc"

			limit="3"

			show_future_entries="yes" 

			show_expired="no"

			} 


			{gs_event_listing_short}

	    {/pf_event_related_event}

	    {/if}

		{pf_event_related_content 

			status="{gs_status_default}"

			orderby="date" 

			sort="desc"

			limit="3"

			} 

			{gs_content_listing_short}

	    {/pf_event_related_content}

</aside>

{/if}        

However...

If I print the total_children tags outside of the if statement, which I've done inside an HTML comment, the above code works.

<!--{pf_event_related_event:total_children show_expired="no"} {pf_event_related_content:total_children show_expired="no"}-->

I guess this might just be a general parse order thing - and let me know if I'm better off going to regular EE forums to shed light on this one!