Opinion — New Macs

Im working for a non-proift we have an all mac network of old donated power mac 7300’s and 7200’s. We just acquired 2 G3 233’s and are looking to buy or upgrade or something. Who knows when we will do this again, so these machines need to last a while. The associate staff does alot of work in filemaker, the lawyers mainly wordprocessing. But My question: do you recommned the G4 upgrade cards for the 7300’s? are iMacs a good idea? Please any thoughts or recommendations, I like to hear experiences from other mac users.