Only do the lunges and squats once a week, twice at the most. If you do them every day you will overtrain your muscles and not get very good results!

So if you want to try them twice a week, make sure you give yourself 3 days in between to let your muscles rebuild. You can start off without hand weights initially, your own body weight will be enough resistance. I'd recommend trying it with no weights at least the first 3 times (3 separate days) just so you can concentrate on your form and balance!
Once you get the form perfected, you can add hand weights if you want. 5 pound weights would be a good start! Whatever you are comfortable with is fine.
Here is a link to a site about pilates. I got my tapes from this site, but there are many pilates tapes available at places like Target and you might be able to find a nice tape there (that doesn't cost an arm and a leg!)
http://www.winsorpilates.com/dyn.php
Pilates work your abs (and other muscles). It's a great workout!!
Good luck! I think you can reasonably lose 10-15 pounds in the time frame you mentioned. Adding some form of exercise (like walking briskly or jogging for 30 minutes a day) and then doing some light weight training will really boost your metabolism. What do you typically eat in a day? Are you snacking on things like doritos and chips? Do you drink alot of regular sodas? Make sure you drink plenty of water!
Check in here often! We'll do our best to support you!

Never give up, you can do it!!!
Oh, I forgot to say this. Do three sets of 10 for each exercise. So do 10 squats, then rest for 30-60 seconds, then do another 10, then rest, then another 10. When I do lunges, it's easier for me to just do one leg at a time. So I will do lunges with my left leg first and then switch to the right leg and then take a break. So do 10 lunges with your left leg, then 10 with your right, then rest for 30-60 seconds. You can rest LONGER between sets if you want to, of course, but try to rest at least 30 seconds.

Good luck!