"We will operate as a family cafe-restaurant," she said.
"We'd be open Wednesdays right through to Sunday evening, but we've really got such a wide range of things we can potentially do.
"Small weddings, birthday parties, high teas, and what I'd like to do in the summer is make up picnic baskets for people to have picnics in the park."
Mrs Marshall said The Lakehouse would be "the sort of place mums with prams could stop to have a coffee and a muffin", or for kids to come and have an ice cream.
"The theme for the whole place is about the lake so my grandchildren have written the children's menu which is called the ducklings' menu," she said.
"The idea is to highlight the lake and focus on the people that use the park."
Mrs Marshall said they had originally planned to open this month but were now looking at opening in the first or second week of May.
The cafe building was built in 1912 as a tearooms and was known as Coronation Hall to commemorate the coronation of King George V.