It just makes sense to have everything in an app.
The website works great on a mobile, but if this could be easily accessible as an app where there is a simplified version of all your fundraising data and pages, that would be perfect. You can then have it linked to things like Face ID so its quicker to log in. You can have notifications when someone donates so you can thank them rapidly. You could check in on how much you have raised at the tap of an app. You could have inspirational things like 'how much you have raised today' or 'how much you have raised this month' or 'how much you have raised since joining JG'. It could also be linked to apps like Strava which I know you are already doing. You could have a chat feature in any fundraising teams which would enable you to say "Hey Joe! Just seen you got a £100 donation. Well done! Our team total is looking much healthier now" (The team I am in for work, I hardly speak to much so this would build team spirit and encouragement). There is so much you could do!
You could even monitise it by reaching out to companies who could add perks... so maybe someone could choose M&S as their perk.. then when they reach 50% of their target, they get a £5 voucher to spend in M&S or they can save it... reach 100% and then get £15. This gives rewards for good deeds and brings customers to big brands.
I am more than happy to keep going with this... but you get the idea.