Croatia is a popular vacation destination and special tourist packages are sold by all major providers. But activating the SIM card and packages is still mainly in croatian, so i suggest to take detailed instructions (found here when available or at the linked websites) with you.
In Croatia there are 3 network operators: T-Hrvatski Telekom, Vip and Tele2. The used frequency bands are european standard.
All major providers are offering special tourist packages, which are still hard to activate without linguistic proficiency. So I suggest to take instructions with you or ask a local seller for help.
Due to a special tax recharge vouchers cost more when the actual balance you get. So double check to buy the correct voucher you need for your selected package.