“Where we can do this procedure and how much the cost for two kids?”

Managing type 1 diabetes in young children is challenging. So far, the best treatment options is flexible insulin regiment, using basal/bollus principles. You give basal insulin for in-between meals (fasting) and bollus for meals based on the amount of carbohydrate consumed. Subcutaneous Insulin infusion (pump) therapy could also be ideal to manage the diabetes. Use of blood glucose sensors would also be an additional benefit. Curing diabetes using using different methods have been tried. One notable advance has been islet cell transplant to the liver using human cadavers. But that requires immunosuppressant medication. This will not be ideal for children. There are other methods in the works. Stem cell therapy is one off them. But so far, we can only wait patiently until its application becomes practical.
So, the answer to your question is you have to wait until it arrives in the future. In the meantime, you will have to review the best available treatment options as mentioned above.
Good luck

Any stem cell procedures for diabetes are experimental. Unfortunately, we do not have a cure for type 1 diabetes yet. However, we are working on it and hopefully will have a cure soon.

Remember that the cause of type 1 diabetes mellitus is autoimmune, meaning that the immune system attacks and damage the pancreatic cells. If you get a "new pancreas" it may work for a few years but always the chance to produce new antibodies exists. I think that we are not yet at the final cure of type 1 diabetes but we are coming closer every year....

Stem cells to "cure" type 1 diabetes is still experimental. Shows good promise. Most of the research is usually done on adults and adults, even with classical antibody positive type 1 diabetes have a somewhat different type of diabetes at times so may or may not be applicable to younger children. Animal research also is promising. At the moment such treatment is still not known to be safe or durable so not a real option but you should discuss with your medical team since they will know more details about your two children, antibody levels etc.