I've done this a couple of times. The first time the sprocket holes got exposed as well - and the only lab near me was a fully automatic one and their machines couldn't produce prints unless they could read the bar codes on the edge of the film. So I just scanned them myself at home. Haven't got prints done coz they were pretty crap.
Another time, I modded the Holga even further and put tape over the insert so that the sprockets wouldn't be exposed. (So it's just like a panorama shot but full negative height.
I took those ones in to be printed, but again it was on the fully automatic machine and they didn't use panorama paper, so the edges are cut off and sometimes the middle of the frame isn't in the middle of the paper.
I tried to scan them in the negative scanner we have but that didn't work because it's made for 35mm size. So I just scanned them on the normal scanner settings but I haven't converted them to normal colours yet.
You could probably try and ask the lab to include the holes but depending on their exquipment it might not be possible to do it.