You can definitely make the flavored cream cheese ahead of time! In fact, it tastes even more flavorful if you let it sit in the fridge for a while; at least 1 hour, or up to 2 days. To store it in the fridge, just make sure it's tightly covered so it doesn't dry out. If the cream cheese has been in the fridge for over 1 hour, let it sit out at room temperature to soften for 30 minutes to 1 hour before using it. And although the canapés taste the best when served right after assembling, if you need to, you can loosely cover the tray of finished canapés with plastic wrap and keep them in the fridge for 1 - 2 hours before serving. The bread may get slightly softer but if you're using Mestemacher bread (or other firm, dense bread), it should still hold up well because it's so hearty. If you're using a very soft, tender bread (like white bread, for example), I recommend serving the canapés right away so the bread stays crisp.