+xAs the part looks fairly small, could you not infuse a flat panel big enough to cover both sides of your intended foam core and bond these around it? Shouldn't be overly time-consuming and the only excess resin would be that used to coat the back of the infused panels and/or the foam core.
You could then look to use foam without the added channels
That would have been ok with this part for sure. For the remainder of the parts they are more complicated and larger, also, the remainder of the parts will include a mold and will require larger vacuum bags and mold preperation