First, please make sure that your computers can boot from CD - that's a BIOS setting, so you need to enter the BIOS (the way to do that is indicated immediately after starting up the machine, *before* the actual OS boots) and set it up to boot from CD as a first (or second, first being floppy) boot device. If you can't get that to work, you'll always have to use boot floppies, and not all of the recommendable distributions offer them.
The question of what to run is crucial - but the most important thing is not CPU, but RAM: What you can use on those machines depends on the amount of RAM they have, so I'd suggest checking that first and stating it here; I can give only preliminary advice before I know what we're really dealing with here.
What I *can* say is that there's a distribution called DeLiLinux
that is very likely to run on both boxes (almost) regardless of RAM, but it's not a first choice - while it's extremely (or rather, admirably) compact and does need only minimal resources, it's also pretty bare-bones and less extendable than other distributions.
You can also start using full featured distributions like Debian
(I'd stay away from the likes of Ubuntu
with such old hardware - it won't work nicely), and there are ways to make them perform well even on very old systems, but frankly, that's not really something I'd try as a first experience in Linux (if you're not willing to learn a lot and do a lot of trial and error). However, those projects offer boot floppies and sport really great documentation and big communities.
You can try interesting distributions for older hardware, starting with DamnSmallLinux
which is already considerably more usable out of the box than DeLi
since it ships with a couple of more common applications and is generally very flexible (but sometimes needs a thorough hands on), Puppylinux
(runs well with 64MB RAM - if there's swap space available, anyhow) and - if there's 128MB of RAM or more - Zenwalk
and Vector Linux
(use the Light
edition of the latter in order to get a usable system. Other possibilities with 128MB+: Xubuntu
(a little lighter than Ubuntu
) - you may have to chose the "alternate" install CD), Fluxbuntu
(they offer a nice RC, but it's clearly work in progress) or Shift Linux
(with a very light GUI, but well done in all). Finally, there's Debris Linux
which works well with 128MB but really takes off with 256MB.
Of those mentioned above, apart from DeLiLinux
(which I like, but would not necessarily recommend because of its quite peculiar set of applications - it takes a lot of getting used to), I'd recommend using Puppylinux
(I run it on a P233MMX with 64MB RAM - fits perfectly!) or Zenwalk
(it *flies* on a PII450 with - well - 384MB RAM, but I already had it running sufficiently well on the very same P233MMX I use with Puppylinux
now). I've also done a customised Debian
install on an old Toshiba laptop (Celeron300 with 192MB RAM), but that certainly didn't run "out of the box" (did take almost a day of tinkering and optimising - but it was very well worth it).
Sorry for the long answer - I hope I didn't confuse you too much