Alright, bear with me here, I might take this a bit off-topic but I'm not judging here, I'm interested only in debating tactics...
So, what would be the purpose of trying to sneak your infantry up against a well concealed, known tank position, supported by dug-in infantry, in the first place? Unless you got an ATG, or tank, or both, of your own covering the infantry advance ready to knock out anyone the inf draws fire from...
Anyway, sneaking up on a known enemy position might work better if you distract them from a direction other than the one you plan to sneak up on them from, I believe.
Say, you're planning a platoon sized attack on the target you described earlier.
Take two squads(an MG and mortars would be fine two) and have them move up the target as obviously as possible with the purpose of frontally engaging the enemy as soon as they spot them, or as soon as they're spotted. When you successfully manage to tie the enemy down in a firefight from one direction, you can try to sneak the third squad behind the enemy and have them assault from that direction for maximum effect.
Personally, I'll try to use the ground to my best advantage, and use hunt till I'm a short distance off the launching point. I'll then slow to the launching point which is as close as possible to the enemy and then I'll break into the assault from there. I have noticed that more experienced units will generally handle all aspects of such a mission much better than greener ones, for sure.
Another thing is, I almost always assign a 1m circular target arc to the unit that does the sneaking part exactly because I don't want them to engage anyone or anything prematurely.