Create a couple of SQL Server agent jobs where each one runs a particular proc.
Then from within your master proc kick off the jobs.
The only way of waiting that I can think of is if you have a status table that each proc updates when it's finished.
Then yet another job could poll that table for total completion and kick off a final proc. Alternatively, you could have a trigger on this table.
The memory implications are completely up to your environment..
UPDATE: If you have access to the task system.. then you could take the same approach. Just have windows execute multiple tasks, each responsible for one proc. Then use a trigger on the status table to kick off something when all of the tasks have completed.
UPDATE2: Also, if you're willing to create a new app, you could house all of the logic in a single exe...