Replatforming possible issue with Submitting URLS

[RocketWeb]

We are replatforming an ecommerce site and will need to change 90% of the urls.  Many current urls contain uppercase characters and the new system forces all lowercase.  We are concerned with submitting the urls all at once to google it might look like spam, receive some sort of penalty or negatively affect organic search. In the last month this site received 428k unique visitors, 3.2 mil page views and has about 10k urls.  They are a top 3 competitor in their vertical.

We are certainly planning to do all 301 redirects.

What can we do additionally to reduce the risk of penalties here?

[LynnPatchett]

Hi Matt,

When you say submitting urls to google I assume you mean via a sitemap in GWT? If so there is no reason for the url changes to cause any issues/penalties - you already have a sitemap with the old urls right? So the new one would have a similar number of urls simply with different paths to the same content... no problems there.

The biggest threat to organic traffic is not having complete and proper 301 redirects in place for all (or most) pages which can potentially cause quite a bit of damage so make sure you have covered all the bases for the 301s!