Hi Chris and
to the forums!
Your little ones are adorable and I can certainly believe you're smitten with them already!
Coco is definitely a male, as you said. With Roo, I can see why you're confused. The shape of the cere is very much male, but the coloring, with the paleness around the nostrils, leads me to believe female. Roo is still very young, younger than Coco. I would wait another week or so and then see how the cere colour has changed, if at all. It would be great to see more photos then, as well!
Regardless of their genders, it's actually quite easy to prevent budgies from mating by making sure not to have any places in the cage which could be seen as a cozy place for making a nest - which is a good practice to follow even in a cage with all males. No coconut hut toys, nest boxes, etc. Also, frequently rearranging their cage will also generally keep them on their toes enough to not give them time to think about nesting.
You can read more information about that in this link:
Meanwhile, you've come to a great place to learn even more about the best of budgie care practices. Please be sure to read through other links on the forums, including the budgie articles and "stickies" at the top of each subforum, to ensure you're up to date on the best of budgie care practices. If you have any questions after doing so, please be sure to ask as we'd love to help~
I hope to see more of Coco and Roo around the forums soon! They're precious