I'm expecting my housemate to be ok with us using her boardgames at a boardgames night that she couldn't attend
Why do you think she will be okay with this?
Because I did her a favor by taking her clothes to the dry cleaner.
It makes sense that because you did a favor for her, that she should be willing to let you use her games. However, I still think you should ask her, to make sure she doesn't have any problems with it. She'll probably say yes and you'll be able to enjoy game night.
I shouldn't have to ask. If she doesn't want anyone to enjoy her fun game then she definitely has some issues.
Even if you are right, you still should ask. It is just common courtesy to do so.