Ya, we can see your decks by just clicking the "My Decks" link under your avatar here on the forums.
Once you know what format you'll be playing at the tournies (Standard, Modern, etc.) if you want to be competitive, look online for winning decks in that format. Check out mtgtop8.com which collects and sorts the winning decklists from tournaments.
Take a deck that looks fun, and start building it. Once you've been playing it a while you, and you really know why each card is in there, then you can start tweaking it as you see fit (because by then, you'll be one of the 'experienced players')
The truly competitive decks usually have some expensive cards, so based on your disposable income, it may take you a while to put it together. A lot of the expensive cards have less expensive alternatives that you could play in the mean time. However, the more you play with those versions, you'll realize that they are cheaper because they're less effective.
Also, start attending Friday Night Magic at your Local Game Store (with your son!) to get into the tournament mentality. These tend to be a little bit more forgiving of deck choices too.