If your son is going to be recording on a laptop, then you will need a USB or Firewire based soundcard. Pick your poison. I have heard less complaints about firewire soundcards, but not all laptops have firewire. If that's the case, then you are pretty much limited to a USB soundcard.
With that in mind, you will need to KNOW how many "Ins" your son will need at any given time. It comes down to, how many different things are going to be "played" or sung at a given time during recording. If he is only going to "one-man-band" it, like most of us I'd guess

, then he may only need 1, 2 or maybe 3 "ins". I am good with only 1 in myself. I play my guit and record it, then I sing and record it, then the Bass etc. etc. All this is tracked and recorded in a software-based mixing board. But, your son may want to play his guitar, mic'd with 2 mics, and sing at the same time. Or maybe he wants to record a drum kit. I don't know. So, in order to pick a USB-based soundcard, you will have to know how many "Ins". Anything from M-Audio is good, IMO. Make sure the soundcard can do at least 24-bit/96,000 Hz. The plus side to this, is that the soundcard/breakout-box will most likely have pre-amps to bring your mics up to line level and phantom power in order to power a condenser mic. MIDI and SPDIF are two other connections to look for. MIDI for sure. These are features I would look for in a soundcard in your situation.
If your USB-based soundcard solution has enough "INS" and pre-amps, and phantom power, I really see no reason for an outboard mixer. Once you have a soundcard that meets all your sons needs, then it'll be time to look into software, then a decent microphone/s. There are many opinions on software and microphones. Once again, it comes down to what you are planning on doing with it. If he has a keyboard, or a drum machine, or is planning on using MIDI, you will need sequencer software. Anything with Sonar from Cakewalk will be useful. You can always go down from there. If he is just going to record audio, the above mentioned Adobe, or N-Tracks are good, inexpensive starter software. Always check Ebay for software first. That's what I do. Or for anything really.
For your microphones, there is an entire forum on this website dedicated to them. Plenty of opinions about what are the best price/performance mics. Think of a dollar amount you plan on spending, then search, or ask. You will get some GREAT opinions from folks actually using, and recording, with the mics they suggest.
Hope that helps.