One question is whether they have asked you to speak for 15 minutes, or whether you have a 15min slot in which to speak? If it is the latter, I would allow some time for questions, and mention up front that you have done so. In your case, I would then hedge my bets incase noone asks anything, by having a few questions prepared, examples include
- if there were no budget limits what would I add
- if the budget were severely limited, what would i do, maybe postpone or reduce
- if the team were bigger etc etc etc
Lets you add slightly outside the narrow brief things,, ideally to personalise it to the situation that you dont yet know the details of...
I would also have tried the speech out several times, so i i would know how fast I was supposed to speak. Having the confidence to pause, especially at first, make eye contact with each person in turn (or a few selected placed about their heads if there are many in the audience comes over well and avoids that terrible 'speaker puts head down, gabbles through speech and then looks up...
Absolutely agree to the structure a PP outlines about, say what you are going to say, say it then tell them what you have said.
Don't be reliant on your slides, but thinking through what they would be (not just a text version of what you are going to say) helps with the structure and helps me to remember the order in which ti say my points.
Oh, and breathe. All the very best