Be aware that in some places between Cancun and Tulum, debit and credit cards are not accepted.
Always have some cash on you. In my case, I always keep around $3,000 pesos on me. I put $1,000 pesos in my right pants pocket and $2,000 pesos in my left pocket. I always pay for my purchases with money from the right pocket. When the right pocket is almost empty, I go to the toilets and put again the sum of $1000 pesos in my right pocket.
It is now easy to check on your cell phone the money withdrawals you have made. A good way to make sure no one hacks into your debit or credit card is to always take the same amount each time you withdraw from an ATM. For example most people will make withdrawals of $500 or $1000 pesos and there is a good chance that a criminal will do the same thing. You could choose an amount like $650 or $1100 pesos. In the event that an amount does not correspond to your withdrawal, you can contact your banking institution and follow the procedures they will give you.
Regarding tips, many restaurant workers have a very low base salary. So they need tips to live. As a general rule if you have received excellent service in the restaurant you add a tip of 20% and otherwise a tip of 10%. It is also customary to tip 10% to people who give you a service, such as the packer at the supermarket or the attendant at the gas station.
Have a good trip