I stayed in Jury's Inn when I visited Old Trafford (my one and only visit - bringing a young ManU fan, not one myself!). It's not walking distance, but is close to the tram which brings you very close to the ground.
Room would definitely be suitable for 1+2. Check their website
I stayed in a travelodge/travellinn in Salford very near ground overlooking the water there think it was a canal. Cant remember which of the two it was it was a few years ago I am sure someone else on the site will know, good luck