On the river you lose 2 bets when you are beat and (should) win one when you are ahead. Questionable if you get this much action from all of OP's 7s. I do, on the other hand, like a river raise for image reasons. It is early in the tourney and you dont want a tight nitty image. Given the low blinds and that you have a playable stack, even if losing two extra bets, I am willing to give up a fraction of BB to possibly get more action later.