You ask a very tough question... and obviously for a good reason. Church budgets today are stretched to their limits and money must be used with wisdom and great care.

My advice is to explore all possibilities including using a Computer and associated hardware, firmware and software. In that regard, take time to explore Band-in-a-Box used by many of the participants here. From my perspective, it would probably have a steeper learning curve unless one of your participants is already familiar with all it's versatility and options.

Being an arranger user, (Yamaha PSR-S970) I am totally prejudiced in that direction but it also takes a bit of time and effort to achieve proficiency. "Quitpic" provided you with one of the many benefits Arrangers can provide. When and if you go to a music store... don't expect much help from the sales staff. Most of them don't have the foggiest notion about arrangers and what they are capable of doing.

Best wishes for success. If you discover other questions during your research, don't be shy. This is a great place for opinions and advice.