As someone who’s studied in Nutrition and many diets, as well as those regarding children, soylent (while not ideal) would be way way better than pediasure, but not just because of the sugar.
Pediasure uses lower-quality fats which aren’t as healthy for any human (including kids) and the protein source they use is bovine-based (cow-milk) which is linked to early onset puberty, which to sum it up real quick causes many years to be taken off the child’s life long-term and promotes acne, hormonal issues, etc, later on.
The downside to soylent is it doesn’t have much resistant-starch or phytonutrients, but those can only be achieved by vegetables/fruits, which pediasure has none of (slightly less than soylent).
Soylent only, ideally don’t do that long-term (or preferably at all unless they’re sick and prefer it), however it’s way better than pediasure or most snacks you can grab real quick, and unless y’all eat very clean meals and lots of vegetables it’s probably a little healthier than what they generally eat tbh, Soylent has a little high protein for kids and they could use a little more fat (preferably from avocados or walnuts) so if they have it often it wouldn’t hurt to cut back a little on their protein intake, or be more relaxed about them eating high-protein parts of a meal as soylent has a higher than needed ratio (unless they’re teenagers 14+).
I never thought to really give soylent to kids, but now that you mention it I’ll begin recommending people with kids I know who are often on the go to give it a shot
EDIT: Just to be clear though, I’m speaking of ages toddler and above, below 1yo they shouldn’t really have anything BUT (human) breastmilk, although fruits are fine too, soylent would be acceptable on occasion but I can’t recommend it as a baby formula as I haven’t looked into it that way.
Briefly looking it looks similar and is acceptable, but I am not going down all the nutrients so unless you do I wouldn’t take that chance as the ratios are likely off for literal babies.