Most of the trips run about $60 US per person. Ocean World and Outback Safari as well as others have excellent websites which give you prices.
Temps - should be hot - about 29 - 32 C during the day in June.
To buy potato chips or Pringles in the DR is very expensive. In Playa Dorado, I think I saw Pringles for $6 US a can - we pay about $1 US here. Snack items like that are about all we take so that we can have them with a drink in our room as we relax.
At an all inclusive, there shouldn’t be a lot you will need to buy - maybe extra for lobster and/or better quality of wine. Everything else should be included. That being said, there may or may not be a charge for safety deposit box, any spa services, but, these can be charged to your room and then settled with your credit card at the end of your stay.
The US dollar is widely accepted in the DR. Tipping and shopping in town can be done in US.
We always bring an insulated mug with a lid so the ice in our drink doesn’t melt so fast in the sun. In the morning, we like lots of ice cold water and later rum & coke. If you go down to the beach, they also keep the sand out. It has NOTHING to do with sanitary conditions at the hotel.
As far as tipping - that is an individual thing. If someone is doing a good job, a tip is in order. If they are rude, why would you tip… same as at home. When in the restaurant, you do not pay for the meal but, we do kind of figure $5 US if an a la carte - maybe $1 US in a buffet if water, coffee or (in evening) wine glass kept full.
Hope that helps - haven’t stayed at that particular hotel so cannot say specifics.