For the two of us (70 year old adults), I prepay gratuities, never buy drink packages, gamble little or nothing. I generally plan on $150-200 per day, including shore excursions, meals, shopping, etc. $200 x 7 days = $1400. Your $3500 for a 7 day cruise sounds like overkill to me, but you do you. My splurges come on winter ski trips.
The old adage is pack your bags for your trip, then take out half your clothes. Fill the empty space with money. Then you are ready to sail.