Hate to be a downer, but "free" boats can get really expensive quickly. It will take a lot of time, effort and material to fix that, by the time your done likely it will cost hundreds of dollars, maybe more. Sails, lines, rigging, maybe an outboard engine, anchor, safety gear ( lifejackets, horn, radio) add up.
Boats are avaiable in sailable condition with all that stuff for not much money but you might have to hunt around marinas, ask other sailors etc.
The trailer looks like a good deal, maybe junk the boat and find one closer to ready to sail for $1000 or so that you can use right away to take the kids and yourself out sailing.
Remember the time/value of getting the family on the water while kids are are young (assuming the girl in the photo is family). Sailing on a boat is way more fun than watching Dad work on one in the driveway!
Here's a Catalina 22 from SBO classifieds that will fit on that trailer just fine -
https://catalina.sailboatowners.com/classified2/adsmanager.php?task=showad&adid=19484