Yes, April UY would be the most ideal for travel at that time.
You typcially want your UY to fall right before you travel as it gives you a lot of flexibility with what you can do with points from a reservation that gets cancelled more than 31 days in advance. Since you have 8 months from the start of your UY to bank points, traveling toward the beginning of your UY is good.
I travel in the summer (I teach) so I have a June UY. It allows my vacations to take place near the beginning and if I ever had to cancel a trip, I could still bank the points, or have time to try to rebook the trip during school vacations.
UY is simply the date that your points kick in each year and determines your banking deadline (for April it would be November 30th)
It plays no role in when you can book your vacations. You can alway book your home resort 11 months in advance of check in, and 7 months out at non home resorts.
Good luck!!!