Do what your heart's telling you...
I strongly suggest that you keep your 4Runner with the following reasons:
* 4x4 is almost a must to have, living in Minesota. I could not imaging driving in snowy day with 4 & 1 years old kids in the back without it - IMHO.
* With two kids, nothing is big enough, but your 4Runner fits the needs, beside you still have plenty of room in the back for your 70 pounder.
* You have already invested some $$$$ on her, it would be a waste getting rid of her now.
* It's probably paid for already, why spending 12k-15k for another vechicle. You might be able to get her fixed up with way less than that.
* It sounded like you still love her, which is also important.
* The list goes on...
But, if you really really wanted to get rid of her, how about selling her and get ...
* A clean, rust free, low mile & mechanically sound 2008-2009 4Runner
* A Hilghlander, like others have suggested, but I think it's too small for two kids in the back... and the dog.
* Honda Pilot with entertainment system, so the 4 & 1 years old will not keep asking you, how long you have to drive, i.e. something to keep them occupied.
* A clean, rust free, low mile GX470. It will keep you going until the wheel fell off. You might not like the 4.7L, which could keep your wallet empty most of the time - depends on how you drive.
... the leak is pretty minimal...
That's a safety hazard, fix it ASAP. While it's not fixed, don't take her out for a long trip.
Do more research, test drives, get your wife involved then decide... whichever vechicle makes you & your wife happy.
Good luck
Cheers!