How much older/slower are the laptops. What sort of spec are you talking about?
DSL, Puppy and Vector will are OK on a 400MHz PII but don't work very well on 120MHz P1s. Even Fedora9 is not too bad on a 400MHz PII.
For P1s, you need something really old like RH5 or SUSE6 but it is next to impossible to find them on the net. I got mine from a book in a 2nd hand bookstore. I haven't found any new distros that work well on really old laptops with 32-64Mb RAM.