I agree, start with no limits. Every team needs to find its own pace.
Surely more than one won't agree with this, but I've had standups that were in a meeting room, "seated", and up to 5 minutes per person.. this team was a really small team, and the stand up helped not only for the reasons already known, but also to build a "fellowship".
In closing, do whatever you need to keep your team comfortable.
Something that it helped at first was asking each team member to fill a shared Google spreadsheet with these columns: [date, finished yesterday, working on, to be finished for the next standup, blocking]. This helped to gain some focus before the meeting, and allowed the team to keep some tracking information.