RE: Is it too late to CD?
You can certainly save money BUT it depends on how you go about it.
If you use prefolds, you can get 2 dozen premium size prefolds for your 17 month old for about $45. Your 3 1/2 year old may be able to share these, at least for daytime, in which case I would get 3 dozen premiums. But the 3 1/2 year old may need to wear toddler size prefolds so you would probably want 2 dozen of those too. You would then need about 4-6 covers per child. If you use Proraps and get seconds (by calling their 800 number), the covers are about $4 each. if you buy them "new", they are about $6.50 each. This has GOT to be cheaper than disposables.
If you decide to use fitteds or AIOs, then you can still save money. Remember that diapers actually have great re-sale value on eBay and other places. You can usually count on getting back at least half of what you paid originally.
HTH,
Beth, mom to older DD (8/01) and younger DD (10/06) and always missing Leah (4/22 - 5/1/05)