Go to party stores and they have a huge array of little give aways and gifts. A cheap but nice gift is take some lacey stuff I forget the name of it.....its like a buck or two a yard, take either some jordon almonds, little rattles or bottles, whatever you like. Then you can wrap up your goodies in little bags and to tie it you can use a little bow, or you can get ribbons with like the parents names or the babys name or whatever. theyre not that expensive, I had them done for my wedding, and it looked real nice and was pretty cheap! And with the ribbons you can get some little minature flowers or berries and either tie them or hot glue.
They also make little minature bubble wand and bottles. Theyre for weddings, but I think they would make a cute little gift too. You can tie those on to the baggies as well.
For lets say 20 people, it would probably only cost around 25-45 bucks, if that.
Oh I just noticed it was for 51 people! I think my suggestion would be easy and affordable, cost should still be no more than maybe $50-75 for that many. I had 50 custom ribbons and it was like $25-30 dollars.