Old Parliament House

Enjoyed a great self guided tour through Old Parliament House.
Fascinating seeing the earlier 'corridors of power' and earlier offices of the PM along with the House of Reps and Senate. Good displays on various individuals, collections and when I went, a display called Dress Code: Empire based around a coat of Sir Edmund Barton.
If you have little people, there's a great play area for the kids divided into three rooms which is really popular (great wet day activity if you're based in Canberra.)
Also enjoyed lunch at Hoi Polloi. Made a lovely activity of a few hours here.
Highly recommended if you like a little history.
Aboriginal Tent Embassy still situated opposite.

If you've only got time for either a tour of this or 'new' parliament house, I'd actually be tempted to recommend this one. It's far more interactive, especially if you've got kids - and much smaller so you can look through it without getting your week's worth of exercise. Cost is a stunning $5 for a family! Really interesting for not just adults or history buffs, but for kids too. Easy parking and you can walk to 'new' parliament house from here.