Lighting is spot on for the unprocessed shot and your photoshop editing job is also spot on. No issues here with the slight shadows underneath your subjects since that is to be expected and the shot would scream 'FAKE' without them (hint: our eyes and brain
expect a certain amount of shadow to be present!)
As for shutter speeds - you should aim for around 1/125 sec minimum for photographing people to help eliminate any potential blurring from slight movements. If you need to bump up the ISO, then do so - there is no visually discernable quality difference between ISO 100 ~ 400 with the 5D.
Aperture values are subjective depending on what you want in focus and/or how much depth of field you require. If you're shooting wide, this is less of a problem but will rapidly show in headshots with mid-tele (75 ~ 105mm) ranges that are used for conventional "flattering" portraits.
For headshots, adequate depth of field on an FF dSLR such as the 5D is from f/5.6 upwards - this would get eyes, nose, ears etc. sharp for frontal or partial side portraits where the depth from nearest to farthest eye is considerable.
As to your dilemma about softboxes, read
this and then consider if this is what you need or want to acheive. A shoot-through umbrella is often a good alternative.
I'd also advise looking into using gel filters for your lights so you can get creative and funky - great for older kids. Don't be afraid to explore different background types too - one of the most inventive (and easy to create) backgrounds that I ever saw for portrait lighting was this
- A thin hardwood board, about 5' x 7'
- Several dozen empty cola cans
- A fair bit of universal adhesive suitable for sticking metal to wood
Stick the cans to the board in a tight honeycomb pattern (no gaps!) with their bases facing up, stand the board vertically and at light it at angles from both sides with coloured gels on your strobes (blue and red work very well for this), light your subject the way you want them with strobes et voila! Instant unusual background made from materials that you'll probably have laying around.
I wish I could find an example image to show you but I can't for the life of me find it right now.