Scrum best practice is to avoid using too many tools.
Agile methods put individuals and interactions first. Tools aren't important. Read this page to see what the real background of scrum is: http://agilemanifesto.org/
Read this to see more about Scrum. http://www.controlchaos.com/old-site/Scrumo.htm
Note that tools aren't really necessary.
Scrum is a series of sprints (managed with a simple backlog and burndown chart).
Scrum is a daily stand-up meeting (managed with no tools at all).
I don't really know Redmine but it looks like the Scrum Alliance Development Team has several Scrum plugins for it. Others potentially useful plugins are the Scrum dashboard plugin, the Todo Lists plugin, the Backlogs plugin but I can't say if they conflict or overlap with the Scrum Alliance plugins. This requires IMO some further investigations and testing.
- If the team is collocated, don't use a web based tool, use sticky notes on a wall and a spreadsheet.
- If there are good reasons to use a web based tool, don't use Redmine if it's not satisfying.