Lester’s alternative is a good one. And there’s yet one more. follow the Merced Lake trail to a mile and a half below Merced Lake where a cut off trail takes you up a different drainage to Sunrise camp. It’s actually little used and is pretty scenic–but I think Lester’s idea is more scenic, if also more peopled.
By the way, Lester’s route makes for a spectacular early spring trip, although I’ve always started early in the morning out of Happy Isles. The whole hike into Merced Lake is often on granite, so it melts off a lot earlier than people might imagine. Snow in the wooded sections is always highly compacted–no postholing. The same is true for the entire climb  up towards Babcock/Emeric lake out of Lake Merced–absolutely no avalanche danger, and the snow is always compacted. I’ve done this early season for many years and rarely see people–never when day hiking up to Babcock, which for me is the highlight. And for a treat, returning via the high route is great, but can require some navigation skills in snow. Not too many, since I can do it! The high route begins at the same junction as the trail to Sunrise off the Merced lake trail.
There is one potentially risky short section on the north facing switchbacks going up from the three bridges over the Merced river. It may be worth carrying micro spikes for this, and later if you go in snow up towards Babcock.
Needless to say there is a ton of cascading water coming off cliffs the whole way on this hike. Seeing it without the crowds is a revelation.
so don’t tell anyone! Again, this is a fabulous early season shake down trip that is always one of the highlights of my hiking year–with very few people past LYValley.