Mini Tummy Tuck Vs Thermage for Loose Abdominal Skin?

Some pictures would be very helpful to give an opinion, but it is generally safe to say that nonsurgical approaches to loose skin frequently disappoint.  This is especially true if you have many stretch marks  or loose folds.  Excision of the loose skin is probably best solution for most such patients, either through lower abdomen incisions, peri-umbilical incisions, or both.

I am not a big fan of Thermage as the results seem to be underwhelming. Another option to consider is possibly a "umbilicoplasty" where the redundant skin is removed and the scar brought into the belly button. Ask your surgeon if you are a candidate.

In patients with significant
abdominal changes following pregnancy, non-surgical methods of treatments are
rarely effective.  Thermage might
create minimal changes, but not enough to make a major difference.  Surgical treatment still represents the
most effective method of treating this problem in the majority of patients. 

I have not been impressed with the Thermage but of course I see the patients who fail treatment and are dissatisfied with teh results. Even a mini tummy tuck may not correct your problem.

Don't waste your money on Thermage. It doesn't work.
A mini-abdominoplasty will deal with skin and muscle issues below the navel only. I see very few patients that are ideal candidates for that procedure.
A full abdominoplasty will give you a flat abdomen but at the expense of a lengthy scar across the lower abdomen... Usually with time, the scar ends up very acceptable, but it is there nevertheless.