Biting off more than we can chew

My friend Ms. Mc loves The Beatles, from the time we met in 6th grade she has always been a fan. She has a set of rag dolls wearing the Sgt. Pepper costumes and she has a tradition of placing her infants among the dolls, as the fifth Beatle so to speak, and taking a photo. Between us we have 5 sons. When this occurred to her last year she suggested that we dress the boys in Sgt. Pepper costumes for Hollowe'en. This year with her 12, 5 and 2 year old and my 4 year old we could have the whole band and my baby could be the 5th Beatle. Upon further reflection she decided that her oldest probably doesn't want to dress like the babies and would prefer something more scary.
After creating a duck costume for last Hollowe'en, I decided we could make Sgt. Pepper's costumes for the boys and add the embellishments ourselves. After perusing the internet to check on prices for professionally made Beatles costumes, and not finding any in children's sizes I realized that making them would be our only option. But I did come across this site which has incredible detail in recreating the Sgt. Pepper's Lonely Hearts Club Band uniforms. I mean really tedious, specific detail. We certainly won't need to be searching for sources of pre-1965 London Fire Brigade buttons, but it will help us get the general look for each band member. On another site a poster recommended using the Simplicity pattern #2561 if adapting the costume for children.
With this information in hand Ms. Mc and I headed to Fabric Depot last week to start by buying the fabric. Yes, we have 6 months before October, but I'm a bit of a procrastinator and I'm already worried we may be biting off more than we can chew sewing 4 costumes for the boys. We were able to find satin fabric in all the neon colors we need and Ms. Mc was able to get a 40% off one item coupons for us. We have The Beatles divided up like this, her two boys will be Paul and George, My Little Helper will be John and the baby will be Ringo in hot pink.
Next step: prepping the fabric and cutting out the pattern pieces!