Always the planner never the bride...er, mom! Help me turn my baby shower excel planner into an app

This app helps you set the ultimate baby shower planning time line based on the baby's due date. Generally starting 8-10 weeks out, it helps you identify the right tasks, sequence them, and plan without getting mommy or her planner friends stressed out.

Minimalist feel. Nothing frilly.

EZBABY Shower

Screen 1 - Welcome.
This screen is simple with an entry of the Baby's due date which uses a simple formula to calculate the subsequent planning activities. Once the baseline list is populated, the planner(s) can drag/drop tasks from one place to another or add any other tasks as desired.

Would like a count down until baby shower incorporated. Would like to launch Google calendar, iCal, Outlook calendar and prepopulate reminders for each of the milestone activities.

Screen 2 - Budget.
This screen displays the committed budget contributions from Grandparents, Parents friends and other family members. The intent is to track the funds in, budget it against key elements of the shower (i.e., invites, food&beverage, decor, favors, cake, games, gifts&prizes) and allocate whose contributions were used against which items (for thank yous etc.)

Would like a budget over/under 'countdown' included. If possible, would like paypal, venmo API tie-in.

Screen 3 - Guest List / RSVPs
This screen would have a list of the guest list and their RSVP status. Would like an API tie in to evite, facebook event and the ability to manually update, should the planners opt for traditional mail invites.

Would like a rolling headcount of guests.

Screen 4 - Day of Timeline.
This screen generates a template timeline for a 3 hour event + set-up time. It is editable by the planners, but gives them a starting point and includes: duration, start, end, activity, responsible person

FYI this contest is for app design, but below are the APIs that will be tied in later:

File Storage - Enables the planner(s) to upload / attach files from their drives to the app (Dropbox, Google Drive, One Drive, iCloud)
Photo Sharing - Enables planners to share photo from the event (Instagram,
Facebook, SnapChat)
Idea Boards - Enables planners to share / create photo ideas for the event to the app (Pinterest, Google photos, iCloud)
Calendar - Enables the planner(s) to add the tasks from the checklist to their personal calendars (Google, Outlook, iCal)
Payment - Enables the planners to send/request money associated with a cost (PayPal, Venmo, Cashapp; Tri-Count tie-in is nice to have)
Shopping List - Ability to build / launch a list of items to be purchased for the event from the web into an Amazon list created specifically for the shower; would like the subtotal of the value of the list to be applied to the budget" Amazon List / Amazon Assistant
Gift Registry "Ability to build a gift registry on the top baby registry sites/web services (Target, Babylist, BuyBuyBaby, Amazon, "Other"); perhaps it's a link to launch the registries
Ability to pre-populate or suggest the top ## items that need to be on a registry (non-brand specific)
Invites - Ability to link to sites that create a virtual invite for the shower (Facebook Invite, Evite, Paperless Post, Punchbowl, Pingg)
Messenger & Email Sharing - Have the ability to share direct links to specific elements of the app; the recipient can click the link and be taken directly to the element within the app (after logging in)
>Share via native text apps to phone
>Share via email apps on phone (Outlook, gmail, Ymail, Apple mailbox)
>Share via messenger apps (Whatsapp, Facebookmessenger, IG)