Activity for Lauren

I've seen on Pinterest where the bride and groom have a box or jar set out at their reception, and the jar is to collect funds for their honeymoon. I like the idea in that it allows you to get a little extra cash. However, is this tacky to do? I mean...

I have no idea what to do for wedding favors, or if they're even really necessary. I'm getting married in early october, so I want favors that have to do with the fall colors or leaves. But, my FH and I are on a super tight budget. The only favors...