The AECR are in a complicated position by being anti-federalist and wanting to largely limit the EU to the single market. The fear that participating in the race for the Commission Presidency will legitimise federalism seems to be misguided to me. While sitting out the debate makes sense for Euroskeptic parties who want to dissolve or withdraw from the EU, surely since the whole point of the AECR is that it is not fundamentally EU, but wants to reform it, the AECR should be organised towards winning posts and influence within the EU institutions to make that happen. By running a candidate, the AECR could have influenced the debate and challenged the other so-called federalist parties. Already Juncker's position seems more friendly to intergovernmentalism: having a candidate further to the right (on whose party's support the EPP may have to rely on in the Parliament) could drag the EPP further towards its position.
So what is the AECR's platform? AECR President, Jan Zahradil, says:
"The AECR rejects harmonised taxes, EU embassies and an EU army. We believe in rolling back the EU bureaucracy to a point where it can provide all citizens with the benefits of free trade, free movement of people, goods, services and capital, improved competition and strong families. We are here to speak for the millions of Europeans who do not want to be part of a federal super-state."
The AECR seems to be running more on its principles than on a manifesto per se, but the Parliamentary group of European Conservatives and Reformists (the AECR sits in this group in Parliament) produced an alternative programme for the Commission's work in 2014, so that might be a good place to start.
The AECR makes furthering the single market in areas like the digital market a priority, and talks about cutting red tape. It's identified a "Top 10 most burdensome legislation" that the AECR wants to be changed for SMEs: the Common system of value added tax; data protection laws; general product safety, Measures to encourage improvements and safety and health of workers at work; Posting of workers in the framework of the provisions of services; Procedures for the award of public workers contracts, public supply contracts and public service contracts; Recognition of professional qualifications; Recording equipment in road transport for driving and rest periods; Refund a value added tax to taxable persons not established in the Member State of refund but established in another Member State; and Registration, Evaluation, authorisation and Restriction of Chemicals.
The ECR group strongly supports the Transatlantic Trade and Investment Partnership Agreement and wants more trade negotiations with India and ASEAN. It opposes any legislation on Information and consultation of workers, and wants the reform of the Working Time Directive. Interestingly, the ECR says that "There is a need for a robust single rulebook for all credit institutions in the EU under the authority of the European Banking Authority" (page 9). You can read more about the ECR's position on other areas, like justice and home affairs, the environment and energy here (PDF).
The AECR is running in the election on its free market and anti-bureaucracy credentials, but it's not necessarily running everywhere in the EU. The member parties of the AECR can be found in 12 EU Member States (in some cases it's representation from a Member State is an independent MEP rather than a party). This limits the AECR's chance for success, though as the 5th largest block in the European Parliament has participated in coalitions on some legislation before.