A.K.
Boy, we moms really find gazillions of things to beat ourselves up over, huh? Because we had twin boys and lots of relatives giving us presents, we had too many toys. The living room floor looked like a Tonka truck garage! When I read your title, "Woulda coulda shoulda..." I thought you were going to ask what would we do differently. Well, my answer would have been to have less toys and more tupperware bowls and wooden spoons. Have your boys really been affected by not having these toys? Doubtful. Do all these newfangled educational toys really make a difference in your child's intelligence? After hearing that Baby Einstein's being sued (right?) for false advertising or something like that because they really don't increase your child's intelligence, I'm inclined to think that they don't make a measurable impact. In fact, I've heard from professionals that toddlers catch up to each other at around age 3, and I've heard others say age 6 when they all start school. I honestly think my kids got the most hours of entertainment from of a play kitchen, toy food, a little cash register, and a big box of dress up clothes. The dress up clothes lasted for years of enjoyment...old hats, scarves, a petticoat, vintage aprons, Halloween costumes, men's suit vests, etc., etc. Lots of creative play.
(BTW, I don't think 4yo is too old for a train set. Our kids played with ours for a while but it mostly ended up being a storage shelf. I think your son just wasn't that interested in it.)
I actually think you are better off not knowing what others spend. That way, you have done your own thing and not compared yourselves to others and felt you had to keep up. There's way too much of that, even with the older kids having the best cell phone or iPod... In your case, I truly think that ignorance was bliss! I'm envious!!