I guess it comes down to dollars and sense
If you can spare the dollars, and think they will get used, then it makes sense. IF there's a high probability that they will just collect more dust, then your wasting dollars that could be used for another or current project. I've walked away from a few deals like this because I knew in my head that even though it was a great deal, it wasn't a great deal IF I didn't use it.
I think if they are cheap enough, you could play with them (camping or what not ) and off them when your tired of them and not be out a lot of money. Of course, it depends on how much it will cost to get them back in running condition. Its not like you don't have the skills to fix them. What about cost of parts? Would it be minimal? Might be worth it to play with.
I mean they would be really cute his and her bikes lol. Put a couple of cute little cupid hearts on them..... and waaaaaa laaaaaaa tell her its an early Valentines Day gift lol.