If, by 'Funland', you mean the Ocean Beach Funfair, it won't be reopening because it was pulled down last October:
https://www.youtube.com/watch?v=h89y_82wC9Q
The only fairground attractions in Rhyl, in future, will be solely the few children's rides at The Village Fairground on the central seafront.
As far as the rest of what Rhyl has to offer, seasonal attractions (throughout the UK) usually open just for the Easter weekend and also for the May Day holiday weekend, with full opening for the summer season starting with the weekend which includes the public holiday at the end of May.
Chris