What a tough decision Anna. It is never just as easy as pro s and con s either is it?
Being a teacher, I would also take into consideration how 'balanced' you think you can manage to be with full time work. I know that relieving doesn't have as much security but if you get enough it is still good money and comes without all the extra stresses of reports, meetings, parent teacher things etc etc. I guess it all comes down to the school culture and workload too and whether you can manage it and switch off at the end of the day to still have family time. (and family time that is quality)
Someone mentioned the holidays and that is really true. At least you would know that every ten weeks you would get two weeks at home.
WOuld be great if you could get a permanent part time position like a PRT release or classroom release job or something but like you said it is harder to get that when the school is small.
I think that whatever you decide will be the right one. I know I really miss teaching and having my own class etc. I have decided to stick with relieving until I have had another child and then go back full time later once they are a wee bit bigger but I think it all depends on when you want to have another bubba - like you said. Working for a year and then having another year off later is great too. Such a personal decison and only you know what is right for you. Good luck lovely one!