G3 will be so old it will barely run anything now… It's too old and slow. They will be fine (assuming in good order) with any software that was released whilst it was the current processor range (which is MANY MANY years ago now), but anything newer it will either struggle, or just won't run at all.
G4 will just be fast enough to do most of what you want, but these PowerPC processors are no longer being supported by Apple in terms of software development. The latest OS 10.6 is Intel processor only, and most new software has ceased support for the PowerPC processors too. Basically you'd be buying a technology that is not going to offer you anything going forward.
A Modern Mac with an Intel Processor is capable of doing everything you ask and more. In terms of Microsoft software you want to run, you can either buy the Mac version or run a windows version inside a Windows Virtual Machine (which does require you to buy a copy of Windows too obviously), which means you've effectively got 2 computers in one… Your normal Mac, and a Windows machine too.
Your cheapest option to be honest, is to buy a 2nd hand Intel Processor Machine. They've been around for 4 years now, so there will be plenty out there on the market… Even the most basic of original MacBooks with a CoreDuo Processor will probably be plenty for what you need, and won't have any issues with compatability etc.