Way to go saving a tree! I always found that branches low on a tree were a great characteristic (even branches that low). I always viewed a tree as a specimen if it split real low. Is this a red maple? I would advise you to let those low branches keep growing because they will fill out the tree much better and making it better for climbing later on. If these branches are large and comprise a good section of bark on the lower part of the tree cutting them could leave the tree prone to diseases and cause some ugly looking scars. You can buy a tree paste that will prevent disease and help heal any major cuts.