I know this isn't exactly a ";Sibelius"; forum but I figured there are more well versed sibelius percussionists on this forum than theirs...

I need to notate a fivetuplet figure over a quarter note triplet.  I'm trying to put egg beaters in a quarter note triplet feel.  How best do I input this in sibelius?

Start with your quarter note triplets. Go to the first quarter note and change it to a 16th note. Highlight that note then hit cntrl 5, and simply repeat the 16th's. this should give you five notes to one quarter note in your sequence. Make sure you have the tuplet set to number in the create drop down. I just did it so it should work for you.