As much as i love the 3 Toyota Hybrids I have owned (1xAuris Hybrid, 1xGen3 Prius and 1xGen4 Prius) and find they suit my needs very adequately, I think a Prius would not be for you and your needs, and although not owned or even been in a Prius Plus, I have doubts that would too.
The Hybrids are good on fuel consumption, the Auris is doing 60+mpg in the summer, the Gen3 I had was doing 66mpg in the summer, and now the Gen4 is doing 75+mpg in the summer. They all drop about 10mpg in the winter months - car engine runs more in the cold weather. I find all 3 comfortable, the Gen4 the most comfortable.
If it was just a family of 2 adults plus 3 kids, the Auris would be just ok, the Prius perhaps more so. The Prius plus, giving 7 seats would be better for your family needs, but you do take a hit on mpg (the standard Prius design is more aerodynamic).
Its the carrying potentially 4 adults plus 3 kids that will rule the "standard" cars out. And when you talk of carrying 5 bikes plus 5 passengers your mpg will drop dramatically. Physically the Prius Plus is the one more suited to you but you would have to make a very careful decision, and not just done on a test drive (which you would probably love).
I dont know what your budget is for this "new" to you car is, but I think you need to look at MPV still. Could you keep what you have got (or even purchase a newer MPV), for the bikes/extended family and buy a used Nissan Leaf mark1 all electric vehicle for doing your local runs to school, shops etc. Mark 1 Leaf should do about 140 miles in the summer and 80-90 miles in the winter on a charge - thats a 5 day week running about covered before a charge overnight.
Just my thoughts, though I will have to go and wash my mouth out after talking about Leaf electric vehicles.