Hi Jennifer,
My daughter also really enjoys the pool parties at Walt Disney World resort pools! She has such a great time dancing and playing with the recreation cast members and other guests.
I called and spoke with a cast member at Disney's Vero Beach Resort, who let me know that they do have a pool party on Mondays through Fridays when the pool is open, as well as a DJ by the pool on Saturday and Sunday. The pool at Disney's Vero Beach Resort is currently undergoing a refurbishment, but that should be well completed by the time you arrive in late April.
The recreation activities at Disney's Vero Beach Resort are numerous. From this link, you can download a sample activity calendar for a week's worth of activities to see if there are other recreation opportunities that you think your children will enjoy. As you get closer to your travel dates, you can also call 772-234-2116 to directly inquire about specific activities for the dates that you are going.
I hope that this information is helpful for you, Jennifer. Have a wonderful time planning your vacation, and please do not hesitate to ask if you have any further questions!