I just came to HOD from MFW! We are Loving HOD!
How much co-homeschooling will be doing?
I do a co-homeschool on Tuesday mornings with two friends who are using the Well Trained Mind. They are the age of my second son - 6, first grade. We rotate the teaching each week. On their weeks they teach their spelling lists. On my week I use the spelling list from Beyond. We do math at the same time, but we all teach our own children. They are using Saxon, and we are using Singapore. Then we take turns teaching from the Drawing with Children book that I have from MFW. At the end one of them has started doing a short reading with comprehension questions from their WTM book, which I don't mind. Truthfully though this is more of a 'play' group,with some school in-between play. My oldest is very motivated on Tuesday morning to finish the rest of his school, except for math, before we go. My other children still have school when we come home. So this may not be exactly what you have in mind. I thought I would share though in case what we do helps generate some ideas.
I did one week of ECC this fall before switching to HOD. (We have done MFW K, 1, & ADV). MFW ECC and Bigger are very very different programs. They are teaching very different topics. I think it would depend how many days a week you are doing it of how much you would choose to have one learn from the others program or have them do similar work at the same time. ECC will have a few hands on activities each week, one Bible memory verse, readings of missionary stories, readings from Windows around the World, geography games, etc. The focus is geography and missions. MFW K has a lot of hands on activities, some reading, and a little Bible reading. It has a story time one day a week. I started with LHFHG with my ds6 who did MFWK last year. I am moving him up to Beyond. LHFHG are MFWK are very different programs. But as you can see above we have found a way to get a little school done in co-homeschooling once a week, even though are programs don't line up.
I have found even doing some school in the same room with friends has been really helpful the rest of the week. It somehow rose the accountability bar.
I hope it works well for you!