Am I supposed to push here?

[Ten7offsuit]

PP MTT
Down to about 300 players, top 100 get paid.
Blinds at 50/100.
I'm in the BB with T900.
I have a very tight image at the table, haven't seen a lot of flops and haven't made any big moves.
Loose passive MP, chipleader at our table with T3200, open limps, LAG SB (T1,500) completes. I have 4-5o. I push, hoping to pick up the blinds. I'm pretty sure SB will fold and there's a pretty good chance MP would lay his hand down as well, he laid his hand down to a big pf raise a couple of hands ago.

Is this a reasonable move? Is this the right time to make this sort of move? I'm new to MTTs and I seem to nearly always fail to build a big stack early and just end up getting blinded down waiting for premium hands to play...