Pop up flash? Hmmmmm.....I didn't know my camera had one of those.
I would use a diffused or bounced shoe-mounted flash in that setting.
For lenses I'd go with a zoom that covers anything in the 16-75mm range. The faster the better although that won't matter as much if you're using flash. That gives you quite a few choices:
Pentax 16-50/2.8 or 17-70/4
Tamron 17-50/2.8 or 28-75/2.8
Sigma 24-60/2.8, 28-70/2.8, or 18-50/2.8
You could also use a few primes, maybe a 21mm or 24mm for the wider shot and something in the 70-100mm range for closer shots.
Another option is to use the kit lens for the wider shots and get something longer for the close-ups and portraits.