Quite possibly even more daunting is the fact the former ACT Liberals leader and his wife Ros are preparing to welcome their fifth child.

After 8½ years in the Assembly, Mr Seselja will formally resign next week to focus on his latest campaign after he won preselection for his Senate tilt over Liberals incumbent Gary Humphries.

As Mr Seselja took his turn to prepare dinner for the kids on Monday night, the 36-year-old reflected on how a political life could always be tempered by coming home to a bustling family.

''Evenings at home are pretty special and I always look forward to a Friday night here as well as things like State of Origin on Wednesday night,'' he said.

''I don't know if it's my fair share but I certainly cook from time to time and I like to do other things around the house whenever I can.''

Mr Seselja praised his wife's ability to juggle their growing family with work and study, and said organisation and planning were the keys to a busy household.

''We've both come from big families so we have the added benefit of a large extended family, but people often ask just how we do it,'' he said.

Mrs Seselja said the shift towards federal politics would be "an exciting new chapter of our lives, assuming everything goes to plan".

Her husband said "fighting for ordinary Canberra families" was the highlight of his time in the Assembly. "Whether that's things like housing affordability, whether it's cost of living, whether it's things like fixing our health and education services, that's been something I've been passionate about.

Mr Seselja will give his valedictory speech on his final sitting day in the Assembly on Thursday before departing on June 11 to prepare for the September 14 poll. He will take a part-time consultancy role before campaigning full-time for the ACT Senate seat.

Since winning the party's Senate nomination in a bitter preselection battle against Senator Humphries, Mr Seselja has faced constant pressure from government MLAs to formally resign. He said now was the right time.

"It is the least disruptive because it means by those next sittings we will have a new member of the Assembly. They will be able to have time to settle in."

A countback process will determine Mr Seselja's replacement in Brindabella, with the most likely successor either Tharwa's Val Jeffery or Homelessness Australia chief Nicole Lawder, both of whom ran for the Canberra Liberals in the October territory elections.

Mr Jeffery said on Monday he would contest the countback and believed he had "a fair chance" of claiming the seat.

"If it comes my way, I'll be in there," he said.

Opposition Leader Jeremy Hanson said he would announce a shuffle of his frontbench next week.

Mr Hanson, who took over the Canberra Liberals leadership in February, said Mr Seselja had achieved a lot in 8½ years.

"The Liberal Party's in a very good place here now in the Assembly with eight members,'' Mr Hanson said.

''It's performing very strongly and Zed can take a lot of credit for that. He's taken the party a long way and I'm the beneficiary of a lot of his hard work.''

Chief Minister Katy Gallagher said Mr Seselja had reached the "right decision" to leave but said it would be "a stretch" to say she would miss his presence in the Assembly chamber.

"I was here for his inaugural speech and I'll be here for his valedictory speech and that's somewhat satisfying," she said.

Mr Seselja promised his most important constituents a ''vegetable-free policy'' for Wednesday night's showdown between Queensland and NSW.

''I think pizza for State of Origin is definitely on the cards,'' he said.