My band The Flying Chaucers do a mixed evening of listningy tunes and high energy dancing. I also call for loads of bands who do similar. I think since you have 2 different bands I'd do the concert one first and then launch into the ceili once people are warmed up and have all arrived. Its often difficult to get things going dancing wise early on for a variety of reasons (I'll leave you to guess the most important hic hic) and if numbers are drifting in its even worse.

Have a good night!!!!

Sarah