OK, basically a tummy tuck is like having a c-section. It should take about a month for you to be able to lift anything (including your children) that means no lifting them into carseats, highchairs, etc. or you could bust your stitches.
Keep in mind that a plastic surgeon told me your skin will continue to go back for 2-5 years after your last child.
Like you, I also looked into the tummy tuck because I gained and lost 65, 55, 45, lbs with each of my three children. I am 38 and felt old and fat!
After seeing how high and how prominent the smiley face scar on my friend was, I reconsidered. I was still disgusted with my body and so I joined weight watchers. (you don't have to buy special food and can eat the same thing as your family, you just count "points")
I lost 25 lbs (that I didn't even realize I was holding on to!) I was 5'4" and my pre-pregnancy was 145...I am now 120 and my tummy is amazingly flat...NOT FLAT LIKE TEENAGER WHO NEVER HAD KIDS, but flat like I don't have all that fat and skin sticking out over my pants when I sit down! Also because the weight came off slowly (I averaged .8 - 1.6 lbs a week, my skin went down with the weight loss).
Also, I did have lipo on my thighs years ago and there was a breast lift/augmentation next to me...I thought she was going to die! She was in so much pain. My other friend had one and couldn't lift her arms for weeks (again no lifting the twins) so don't sell yourself short on the amount of pain you will be in. I am still considering this surgery myself.
I know it is a difficult time for you and how you feel about your body...been there done that, but you may want to work on eating well and really getting down to the weight that you want. Once you are there, you can reconsider the tummy tuck. I am glad I did it naturally, and although it took me four months to do it, it wasn't painful at all!