Bending fork
 

So the hubs I just got are spaced a bit smaller than the fork. Maybe 5mm or so. Is it okay to just tighten it down and bend the fork in that small amount? It's a steel fork.

no.
sacrilegious.

yes, it's ok.

With the vast majority of forks, you will find that they are slightly wider than their nominal size, and when a wheel is dropped in, they will need to be drawn in slightly by the tightening of the QR in the case of a road bike, or by tightening the nuts on a track bike. Some of my forks are closer fits than others, but they are all 'off' slightly compared to the standard width of the hub. This is intentional, as too small would be a bit of a pain to install a wheel in, although I did have one like that several bikes ago.

5mm is alot.
does the wheel center up under the fork crown?
if not i would take it to someone to have it checked out. or go to you local bike co-op and see if someone there can help you out.

go get some spacers, 2.5 on each side. easy fix.
but i would say squeezing the fork 5mm should be ok until then.

It'll be fine if you squeeze it, structurally speaking. One thing to note, however, is that the alignment might get messed up slightly that way. If you squeeze it and the wheel still sits straight (i.e. you can ride no-handed without veering off to one side), then you may as well leave it that way. If you crank it down and your handling gets all wonky, then you may want to have your shop put it in a jig to actually bend it properly while making sure it stays straight, or else get spacers.