How can we launch quickly and secure IP at the same time?

Both of the previous answers are correct, from a technical prosecution point of view. However your question was, I believe directed to "have its IP secured" in order to "secure serious funding." Simply filing a provisional will protect you with a early filing date and is always a good idea. However, it will not help you secure serious funding. Investors want to see an issued patent so they can assess the extent of protection. You need to file a non-provisional as soon as possible and follow it up with Continuations-In-Part as you make changes/improvements. This will get the process started, as opposed to a provisional patent which is simply an idle place holder. In addition, you will want to use one of the many avenues for accelerated prosecution. This will unfortunately add cost, but will significantly shorten the often three to four year process of obtaining a patent. Momentum is important, the USPTO recognizes that and charges a premium.