I suggest that you consider the following approach:
1. Disable the scheduling in Veeam (and use task scheduler instead).
2. Use a single powershell script to run the 3 jobs (unless you want them to run at the same time).
See the example I have just posted here:viewtopic.php?f=26&t=13710
Send an email report for the veeam backup jobs.
3. At the end of the script, launch the backup exec script.
Send another email report after the backup exec job (you can use backup exec built in email notification).
4. Schedule the powershell script using Task Scheduler
5. Double check that it works as expected,
Also test and debug for gochas situations such as what happens if the backup exec server is unavailable, if there is no tape in the drive, and other potential problems.
Yet another approach is to schedule the veeam backup jobs at evening, and backup exec to tape during the day, assuming that veeams needs only few hours to complete all jobs.