There are many posts on this touchy subject. I would suggest not using the bumper. Even if it was strong enough (its not) the flex of the bikes hanging out over the bumper is amazing while traveling. You could lose them. The bike rack on the bumper may void frame warranty.
The bumper by itself is not adequate. A number of us have a 2" receiver installed, but with beefed up framing, and have not had problems. But you need to do it properly. Some haven't done it properly and have had problems. Otherwise, other options include the Arvika mentioned above, going with a front hitch on your tow vehicle, carrying them in your TV (pickup bed) or putting your bikes in the RV. Do a search for "bike rack" in the forum and stand by for lots of opinions!!!
1988 Coleman Sequoia - popup (1987-2007)
2012 Roo19 - hybid (2012-2015)
2016 Mini Lite 2503S - tt (2015 - ???)
2011 Traverse LT, 3.6L, FWD
2009 Silverado Ext Cab, 5.3L, 4x4, 3.73
2016 Silverado 2500HD Dbl Cab, 6.0L 4x4, 4.10