Help finding a lens for my T1i/500D please! =)

Hello! All you guys have helped me tons in the past you guys helped me choose to buy the T1i so now I am asking for help choosing a lens for it!

I had the kit lens and purchased the 55-200mm but I quickly realized changing lenses is NOT something I want or am willing to do. I dont need a crazy zoom I was pretty happy with the 200mm although 250mm would have been good too. I take pictures on the beach every year of my family up close then would want to use my zoom also I am not going to switch lenses on the beach and risk getting sand in my camera or my lens. I take impeccable care of my camera so thats why I decided to buy one of the 18-200 "all in ones"

Here are my concerns and questions:

First I was wondering since canon only makes an 18-200mm would it be ok to get another brand of lens that might give me the option to go a little higher with my zoom? I am nervous about that though because I know I can trust canon and have zero experience with any lens companies.

Secondly I know that the 55-200mm had some color distortion and issues at the fullest end of the zoom so I assume the 18-200mm with be the same way. Does anyone know if it will be like that and is there a way around this? If not would buying a different brand lens be a better option of avoid this all together???

Thirdly one of the major things I need this zoom lens is for the shows we go see at Disney etc they are stage shows at night with some lighting but I have heard that the higher end zoom lenses perform poorly in those situations is this true? If so are there other options I should consider or maybe just a way to use the lens to get the best possible pics in these situations?

I am will to spend the money to get what I want for me it will be worth every penny!! The only thing I am absolutely NOT willing to do is switch lenses I hate it and if thats the choice I have to make I would rather go without a zoom then to have to do that in the middle of our family trips! I love my T1i it has been all I could have hoped for and then some now I am just looking for my all in one zoom lens! Any and all help is welcome and will be GREATLY appreciated!!!! Thanks in advance! Kelly