by him being there with Jan, would it be him catching? or Jan still doing the primary care and catching and him just sort of hanging around as her backup?
good luck with making the choice, so lucky you have that sort of professional support around you to give you what you really want!!!
go with your gut, and what you will feel most comfortable. Have you met Jan's backup midwife? maybe meet her and see what you think you can get from her, comfort and support wise.
basically it is what you feel will work best for you, what and who you are most comfortable with and who you think will provide you with what YOU want and not take over the situation.
good luck!!!