Just to clarify, do you want a "good value" studio or a good "value studio"? If you are looking to rent points from an owner, you might be able to get a standard studio, but it is pretty late in the season. I think SSR would be the only thing, and that doesn't sleep 5. I did just add on one night to a Poly studio for Sept 1, but I think I literally got the last one, as now it's not showing any additional availability.
A standard studio at Poly for those dates is 16 points for Thursday and 19 for Friday. Renting it at $15 pp would put you at $525 for both nights. That's not cheap, but not terrible, especially compared to what you'd pay from Disney. With all those little ones, monorail access would probably be pretty nice.
Now you just need to find someone with those dates already booked to rent it to you.
(I ran a search with multiple kids under 3, and it let me select even the studios that only sleep 4. I changed the age to older kids, and then it says "cannot accommodate your party size," so maybe SSR would work. Someone else might be able to chime in on that aspect. If you could get that to work, it would be 27 points, and that reservation is available now. You might even be able to get it at a discounted price per point, since it's coming up so soon.)