My 86 and 91 year old parents still insist on spending summers (4-6 months) in their old family home in a rather remote area of Italy. Luckily some family member has always been available to stay with them but it is a project getting them there and back. Getting wheelchair transport in the airport is essential even if they don't like the idea but they are treated very well and things have gone smoothly. Last week they had to travel from southern Italy to Bologna for a grandtr's graduation. The hotel provided a wheel chair for my father. Although he can walk short distances, it saves on energy.
For the flight over they are sure to stay hydrated, take their aspirin and exercise their legs every hour and get up and move around a couple of times to prevent blood clots in legs. Talk to the doctor before you leave for any specific considerations for them.
Also, for my parents, they really look forward to the rest time in the afternoon to recharge. In Rome, use cabs for them to get around.
For airport to hotel, i once used RomeCabs and they were great. Also, when traveling with a diverse family group, it sometimes make sense to divide up at times. Everybody does not have to do everything in my opinion.
Have a great trip.You will be making MEMORIES!