1. the tandem island is more of a proposition than the A-AI being a much larger boat all round - more issues about storage & transport. From what I have seen it would solo perfectly OK and you would have the flexibility that when your other half decides she wants to participate she'd be able to jump on board easily. It is rather more expensive too which is definitely a factor!
2. if you can't wait to get out on the water then I do not imagine that the AI conversion will be too much of an issue - I haven't done one, but I had to 'almost do' one when my AI hull cracked (outside warranty!) and Hobie gave me a replacement (where else would you get that sort of service??!!!?). I had to take the AI components off the old hull & install them in the new hull and it didn't take much - a day, a few hand tools and a bit of common sense - I imagine that the AI conversion kit involves the same install but with the benefit of some instructions.
3. if you went with the A to start with you would still be able to get into kayaking & sailing with the small sail & daggerboard; this remains my preferred sailing experience on my AI - kayak hull only, small sail, daggerboard, no outriggers. That said the conditions where I live are often ideal (up to force 4 winds & relatively calm seas) it might be a different matter if prevalent conditions are different where you intend to sail. It would, however, give you the ability to learn and hone your sailing skills on a cheaper but more engaging boat that behaves like a 'proper' sailing boat in a way that a trimaran does not; then, when/if you decide to convert to the AI you will know what you are doing! But if/when your wife decides she wants to join you you are going to have to buy her a boat too or trade up to a tandem.
4. if you started with the A and small sail & then decided that you want the stability of a trimaran without the expense of an AI you would even be able to add the 'small scale' akas and amas to your A to get that extra stability - not exactly my cup of tea but, like golf, lotsa people do it, so there has to be something in it
Decisions, decisions ! You gotta love the versatility of these boats and congratulate Hobie on offering so much flexibility between their product & accessories lines
Hope this helps.