I'm in Brighton and it's raining. What can I do with my 3 yr old?

[Tobermory]

We are in central Brighton staying with family who are at work. Having spent the morning in, we desperately need to get out or go crackers! Any options other than Sealife centre? Have a 4 month old as well as 3 yo so location needs to buggy friendly.
We painted a pot yesterday which was great but surprisingly costly.

have you been to ride the horse carosell on the pier? DO you have access to a car? devils dyke is nice.
In my experience though the public transport routes were good and there were a few things to hope on to do. fuzzy brained so cant help more.