the temptation is there to expand the offered package because you want the work.
but i wouldn't take too many photos for 300 dollars...or offer too much in the way of formats and versions. 16gigs of shots is 750+ shots (i don't know if you have a FF cam or an APS-C DSLR.) you'll have to individually appraise most of these, spend some time getting a feel for the best look, then PP the selected ones (sized for web, 100% size for print..and printables are bigger and slower to PP.) etc etc. it's all hours of your time. planning the job is 1 hour. attending is 2 or 3. appraissing is 2. test editing is 1. pping is 3 or 4. supplying the end-product is 1. chasing payment is 1. so that's potential 13 hours skilled work and associated admin for 300 dollars. then the customer says ''yes these are fine but can we have...'' which another 2 hours or something. $17 per hour isn't enough fee.
if you think in terms of $50/hour (which is dirt cheap) and you agree to spend 2 hours at the party, then the rest of the task will cost you $200 which is 4 hours work. considering admin and payment that leaves nothing left (of $300) for your editing time. take 100 pictures maximum. choose 10-15. PP and supply. that maybe take 4 hours..and extra $200. your price is light by at least $200 IMO. $500 for 15 post-produced shots including RAW masterfiles and PP'd 100% size JPEGS.
and even these costings ignore real-world business expenses (bills, insurance, transport, promotional budget, cost of tools etc). this is why professional services need to be very expensive!
I agree with some of the things you said, but 100 shots? Absolutely not. That would be a massive ripoff.
I'm a firm believer in doing your best no matter what the expected outcome. Just because he's only being paid $300 doesn't mean he should do a half-***'d job. Limiting yourself to a small number of shots purely because you don't want to spend too much time in PP is absolutely ridiculous and *TERRIBLE* business practice.
Take as many pictures as you feel comfortable with. Make sure to try to get the best composition and perspective possible...but don't feel limited in how many pictures you take. I'd expect around 200-300 pictures in a 4-hour event, but anywhere from 150-500 should be acceptable.
I've easily taken 300+ in 2 hours depending on the event.