Normally with squint surgery if the deviation from straight is up to about 5 degrees another op won’t be advised, as you may get a consecutive outward stabismus (exotropia) instead of his esotropia (turning in)
Always make sure his spex are up to date and with as much plus power as he can tolerate, this will help to relax his accommodation and mimimise the turn. If he only squints when reading then bifocals or varifocals may help to keep his eyes straight.
If he’s only 2 theres still time before his visual system matures to get good vision in both eyes and some degree of binocular vision.
100% correction can be tricky depending on the case and skill of the surgeon.