Hi F. B. (that name always cracks me up!)
Here's my take on it...
First, some kids do a few 'hmmm...I'm trying this out' times on the potty and then lose interest. Other kids show readiness because they are ready. Is he ready in all the realms he should be (able to communicate need to use the toilet? able to dress himself/pull pants/underpants up and down) etc.
Here's a site I like that can help you assess if now is the right time or if waiting a while (as you were planning) would be preferable:
http://www.betterkidcare.psu.edu/AngelUnits/OneHour/Toile...
I would strongly recommend avoiding pull-ups like the plague. For most kids, they are 'magic underwear' --they look similar to undies but magic because the child doesn't experience getting wet...which is both a natural consequence of not making it to the toilet on time AND a great motivator. Why work to stay dry if the magic underwear does it for you? I've helped a great deal of children potty train and pull-ups nearly *always* delayed the process or confused the child. A regular diaper (even disposable) is better because at least the child *knows* they are 'in a diaper' instead of underpants. Think of it this way: if your child can't tell they are wet without 'alert' chemicals and tabs telling him, which is pretty non-intuitive for a child, this is probably not a great PT product.
(My one time I would use pull-ups is ONLY for outings, when I was a nanny. Then, I called them a 'travel diaper' and this is because some children were attached to the pull-ups/wouldn't 'go back' to diapers and public toilets are often scary for little ones at first. With my own son, we just used diapers until he was able to do regularly go potty during outings.)
Otherwise, I would go the route you suggest, which is trainers and a diaper wrap or rubber pants over them. I personally really like nice, thick training pants. Hanna Andersson makes very good ones that wear forever, so if you are having more kids who will need to potty train, they'll get to use them too, or pass them along to a friend/relative. Even the thick Gerbers really are fine. What you want to avoid is the thinner, BVD type character underwear. That's just going to be a soggy mess.
Nighttime dryness often takes longer for some children to achieve. I'd use a regular diaper for nighttime until the child is regularly staying dry at night.
Also, pick up a couple of the 'plush' waterproof fitted sheets. If you make the bed twice (fitted sheet, top sheet, fitted sheet, top sheet), when you have nighttime accidents, just remove the first set of sheets and voila! you have a made bed underneath.
Good luck and feel free to PM me if you have any additional questions. I do this for a living... ha ha. I have a longer Supporting Toilet Learning piece I was working on for a book that I'd be happy to email you.