there is a tank holder that you can get for wheelchairs- you would just need to stay near your daughter when you are out and about- ask the vendor where your oxygen supplies come from. It attaches to the back of the wheelchair. Also, if this is a permanent thing, talk to the vendor about getting a smaller portable set up- I don't know if that will work for you, but they do have some that are as small as a large purse with a shoulder strap.
As for the 50 feet of tubing- do you always carry the tank around with you when you walk? if so, ask the vendor for shorter tubing. If not, use velcro cable tamers to gather up some of the loose coils of tubing. Good luck and get better :-)