Do the kids fit in the spare tank? Hmm, just a thought...
Marcie, there are lots of very experienced hobbyists in Calgary, most of whom are more than willing to help out newcomers. Maybe someone will offer to have you over and look at a simple sump set up. If you have a spare 72 sitting round (and you aren't going to put kids in it), that would make a great sump if you can fit it in your setup.
Now, I've done the kids thing, and sometimes I just don't have time to do the things I really should do myself, so then I pay someone to do it. In this case you may want to buy that ebay model just for the convenience of it. Sure, you can do better, and certainly could make something similar for way less, but if time is an issue, maybe it's something to look at. And in the big picture, 300 bucks isn't THAAAT much....