I understand your dilemma...I am doing a random scrappy and together they didn't look right so I am sashing them in red. That being said, I think yours will look great "unsashed" (not sure that's a word!). Then maybe a thick white border and then a thin border of individual squares going round, then another white border and bind in red or scrappy.
Whatever you choose it will be really pretty, you have some lovely fabrics there. Ultimately I think YOU have to feel comfortable with the design. Whatever you decide I think it will look great...so keep updating us...you know how we love pictures.