This might seem like a guy activity, but we had just as many girls participate. It’s also a skill that will come in handy.
Spend time showing them how to tie a tie. Don’t get too complicated on the knots. You can provide printed diagrams, but we actually had them find their own instructions online. There are some good printable diagrams online or videos on youtube and other sites.
You can buy ties for cheap at thrift stores.
You can also make a game out of it by having races or judging the overall look of the knot.