Honestly I think you will be okay with United. Heres a trick. There new service that United, and a few other airlines have, they do Curbside Check-in now. Even though this costs a little usually the guys will drop the extra backage charge if you give them a big tip. Usually their staff is even pretty upfront about it, its hilarious.
The first time I used it the guy was like "if you happen to be generous you will not have to worry about extra charges". I was like Gotchya! haha and ran off the ATM. I returned paid the fee then gave him a $20 tip. Keep in mind that I had a shitload of baggage (over the 50lb limit, which I think is an extra $100). Also I had an extra bag (ski bag) which is supposed to be an extra $50. Ended up saving around $130 and a whole shitload of hassle trying to carry all my baggage through the airport and through check-in.