Memory usage of process

Hi
I have a process(root) which spawns other processes to get its work done. These 
children in turn may spawn more processes and so on. I want to obtain the 
memory used by all of these processes at a point of time from the root 
process(very 1st process).
So, I neeed 2 things:

First is to obtain all the process handles of this process tree.
So, Is there a way to find all the child processes for a particular process. 
Right now I am using "CreateToolhelp32Snapshot" to obtain a snapshot of all the 
processes in the system and then looking for the processes which have root 
process as their parent. Doing this recursively to obtain the whole process 
tree.
Is there a better approach available for doing this?

Secondly, get the memory used by process. Is there an API available to do this? 
Can not use "PSAPI" as its not for Win95, 98.

Thanx
kapil