It seems your programming pattern requires turning on the same zone more than once in a program. This is not something not currently supported by OpenSprinkler firmware. You can split the pattern into two programs, but the Program Switch only activates one program at a time and cannot make two programs run one after another.
I think your application is somewhat beyond the standard use of OpenSprinkler. OpenSprinkler Bee (which we released just recently) supports more flexible programming capability which will fit your need, but it only supports three zones. I am considering changing OpenSprinkler firmware to support the same programming capability of OpenSprinkler Bee. But this will take some time to implement.
One possible solution, in the mean time, is to modify the OpenSprinkler firmware to hard-code your splash pad program, so that once activated, it directly executes the pattern you wanted. Another solution, which may be more flexible, is to use a Raspberry Pi, or even an ESP8266 microcontroller, connected to a switch, to trigger the start of your splash pad program. Once started, the Raspberry Pi or ESP8266 will send the custom watering pattern to OpenSprinkler through HTTP GET command. Either case, it will require some programming.