[SalesForce] Cascade delete limits

This code is not correct. Following corrections are required:-

1. There should not be any SOQL within For loop.
2. Also, you can look into minimizing the queries (first query is non-required, as you should already have list of Sales plan)
3. Perform DML statements (update and delete) outside of FOR loop.

Once you modify the code as per above suggestions, it'll be able to handle any level of cascade delete and will also work in bulk scenarios.

Furthermore, I'll recommend you to look into trigger design patterns and make use of it to avoid such issues. I personally like and recommend http://developer.force.com/cookbook/recipe/trigger-pattern-for-tidy-streamlined-bulkified-triggers

I am not writing complete code for you suppose you have

List<Account> accList ;// list of child record which we need to do delete 
if(accList.size() < 10000)
    delete accList;
else {
    while(accList.size() > 0) {
     integer count = 1;
     List<account> tempList = new Account();
     for(integer counter = 0 ; counter < accList.size()) {
         tempList.add(accList[counter]);
         accList.remove(remove);
         count++;
         if(count == 10000)
         break;
        }
       if(tempList.size() > 0)
          delete tempList;
    }
}

As it is not optimize code because it has DML inside for loop but it will work for you. If you have more then millions record then you will hit the limit.