HI There. My son potty trained at 2 1/2 and hated underpants! He would cry when i put them on. So, i gave up trying. However, one day, when it all clicked for him, he requested to wear them and voila, he was never in diapers again. I put the undies in a drawer where he could get to them, and he loved to be able to pick out the ones he wanted. Also, i learned right away, that little bodies have a hard time running in and making it to the potty every time, so i put a potty in a convenient location (it is in the kitchen for my 2 year old right now) so that if they feel the urge and can't make it to the bathroom, they have another option. Perhaps putting a potty outside where it can be easily accessed with out asking for help would make a difference.
Good luck, and remember, before you know it they will be potty trained and these challenges will be in the past.