First Of All, Congratulations!
First of all, congratulations on your forthcoming release, Biggles! The fact that you are committed to a release, in itself, is a bigger step than MANY gifted musicians are willing/able to take, IMHO.
As for song order, I would probably open with a suggestion to try to follow any live performance set list that you have noticed has been particularly successful (if you have, in fact, had experience performing these songs live). If you have not played these songs live yet, perhaps it is time to develop a set list and give it a whirl...even in front of the smallest of audiences, if necessary. There really IS NOT any set formula to look for here, just best bets. Songs whose root key are the same or part of a "natural harmony" tend to go well together and perhaps some thought can be given to that.
Next...tempo can be a HUGE consideration. Not much sense in putting ALL your "up tempo" songs back-to-back and either "sandwiching together in the middle" beginning or ending with ALL of your slow tempo tunes. Some thought should probably be given to mixing the tempo up a bit. This helps maintain the listeners' attention span more effectively too. Especially true for first time listeners who don't know what kind of experience to expect from your repertoire.
VERY IMPORTANT: If you have a song that could be considered a "title cut" to your compilation, if you put the title cut first, it tends to project more confidence and credence to the compilation's "central theme," where a central theme or principal topic/inspiration applies.
As for being up to the band on these decisions? Well, unless someone else outside of the band is financing all this and their sensibilities would be injured to the point of losing future financial assistance from them, I would vote a resounding "YES! LET THE BAND DECIDE!" I want to reiterate, though, that the band should try to base it's arrangement decisions on feedback from your audience(s), to date, as much as possible. Got to put the sentiments of your faithful followers first as much as possible...because they are the folks who have demonstrated first loyalty and appreciation to you...and...if you want them to pay cover charge, buy T-Shirts and other memorabilia with band logo, buy the current and future recorded musical works and sing your praises to others...it is pretty important to let them have the feeling that you put their sentiments first. Remember the old saying, "A thousand Frenchmen can't be wrong?" 🙂
As for singles? Well, as you may know, the reason the "filler song" approach emerged was because if there were other songs that were exceptionally dynamic on that compilation, it would be kind of self-defeating to shoot them out 2 at a time on the compilation, lest ye render yourself a "one-hit-wonder." In my opinion and experience, it is generally best to whet your audiences' appetite, but find a way to leave them "wanting more" at the end of the show/listening experience. Otherwise, the listening experience tends to become somewhat anti-climactic. On the other hand, I would not recommend you "sandbag" the musical work that earns the best "live audience response" from your first single either. The strategy, when applied successfully, is open with your power, and work your way to less power on the CD/record. The reason for this is primarily one of maintaining your listeners' attention span. Remember, you don't get a second chance at a first impression. ;-)
I hope you find this helpful, Biggles, and I am sure that Dave2112, DVNC, MastrTklr, TummyDragon, bass, OneFunkyBassist, and others comrades in music and tickling too numerous to remember or mention in one post can offer some valuable input on the topic, as well.
Please let me know where I can hear samples/buy a copy when the work is finished! I'd love to hear it!😀