I've found that the Public role in msdb has the needed permissions by default, but if someone has changed that in your instance, you can grant EXECUTE to the following stored procedures to the non-sysadmin user:
sp_enum_dtspackagelog
sp_enum_dtspackages
sp_enum_dtssteplog
sp_enum_dtstasklog
sp_get_dtspackage
sp_get_dtsversion
sp_drop_dtspackage
sp_add_dtspackage
The user will be able to execute packages that it creates.
Greg